Glossary of Landform and Geologic Terms, Study notes of Geomorphology

Download Glossary of Landform and Geologic Terms and more Study notes Geomorphology in PDF only on Docsity! Glossary aa lava – A type of basaltic lava (material) having a rough, jagged, clinkery surface and a vesicular interior. Compare – block lava, pahoehoe lava, pillow lava. GG & MA aa lava flow – A type of basaltic lava flow dominated by aa lava and a characteristically rough, jagged, clinkery surface. Compare – block lava flow, pahoehoe lava flow, pillow lava flow. GG & MA ablation till – (not preferred) refer to supraglacial till. accretion – [sedimentology] The gradual increase or extension of land by natural forces acting over a long period of time, as on a beach by the washing up of sand from the sea or on a flood plain by the accumulation of sediment deposited by a stream. Synonym: aggradation. GG active layer – The top layer of ground subject to annual thawing and freezing in areas underlain by permafrost. NRC active slope – (not recommended: obsolete) aeolian – (not recommended: obsolete) use eolian. aggradation – The building-up of the Earth's surface by deposition; specifically, the accumulation of material by any process in order to establish or maintain uniformity of grade or slope; also called accretion. Compare – degradation. GG alas – A type of thermokarst depression with steep sides and a flat, grass-covered floor, found in thermokarst terrain, produced by thawing of extensive areas of very thick and exceedingly ice-rich permafrost. Compare – thermokarst depression. NRC and GG alluvial – Pertaining to material or processes associated with transportation and/or subaerial deposition by concentrated running water. Compare – colluvial. GSST alluvial cone – A semi-conical type of alluvial fan with very steep slopes; it is higher, narrower, and steeper (e.g., > 40% slopes) than a fan, and composed of coarser, and thicker layers of material deposited by a combination of alluvial episodes and to a much lesser degree, landslides (e.g., debris flow). Coarsest materials tend to concentrate at the cone apex. Compare – alluvial fan, talus cone. SW alluvial fan – A low, outspread mass of loose materials and/or rock material, commonly with gentle slopes, shaped like an open fan or a segment of a cone, deposited by a stream (best expressed in semiarid regions) at the place where it issues from a narrow mountain or upland valley; or where a tributary stream is near or at its junction with the main stream. It is steepest near its apex which points upstream and slopes gently and convexly outward (downstream) with a gradual decrease in gradient. GG alluvial flat – (a) (colloquial: western USA) A nearly level, graded, alluvial surface in bolsons and semi-bolsons that lacks distinct channels, terraces, or flood plain levels. Compare – flood-plain step, terrace, valley flat. FFP, GG, & SW. (b) (not preferred) A general term for a small flood plain bordering a river, on which alluvium is deposited during floods. GG alluvial plain – (a) A large assemblage of fluvial landforms (braided streams, terraces, etc.,) that form low gradient, regional ramps along the flanks of mountains and extend great distances from their sources (e.g., High Plains of North America. SW. (b) (not recommended, use flood plain.) A general, informal term for a broad flood plain or a low-gradient delta. Compare – alluvial flat. FFP alluvial plain remnant – An erosional remnant of an alluvial plain which retains the surface form and alluvial deposits of its origin but was not emplaced by, and commonly does not grade to a present-day stream or drainage network. Compare – alluvial plain, erosional remnant, paleoterrace. SW alluvial terrace – (not preferred) refer to stream terrace. alluvium – Unconsolidated, clastic material subaerially deposited by running water, including gravel, sand, silt, clay, and various mixtures of these. Compare – colluvium, slope alluvium. HP alpine – (a) [geomorphology] (adjective) Characteristic of, or resembling the European Alps, or any lofty mountain or mountain system, especially one so modified by intense glacial erosion as to contain cirques, horns, etc. (e.g., alpine lake) GG. (b) (not recommended as a landform term). An ecological community term for high- elevation plant communities. SW & GG alpine glacier – (a) Any glacier in a mountain range except an ice cap or ice sheet. It usually originates in a cirque and may flow down into a valley previously carved by a stream. Compare – continental glacier. GG. (b) (not preferred – refer to U-shaped valley): (relict) – landforms or sediments formed, modified or deposited by a glacier in or on mountains or high hills that has since melted away. Compare – glacial-valley floor, glacial-valley wall. SW andesitic lahar deposit – A lahar dominated by andesitic volcaniclastics. SW angle of repose – The maximum angle of slope (measured from a horizontal plane) at which loose, cohesionless material will come to rest. GG annular drainage pattern – A drainage pattern in which subsequent streams follow a roughly circular or concentric path along a belt of weak rocks, resembling in plan view, a ring-like pattern where the bedrock joints or fracturing control the parallel tributaries. It is best displayed in streams draining a maturely dissected granitic or sedimentary structural dome or basin where erosion has exposed rimming sedimentary strata of greatly varying degrees of hardness, as in the Red Valley which nearly encircles the domal structure of the Black Hills, SD. SW, GG, & WA anthropogenic feature – An artificial feature on the earth’s surface (including those in shallow water), having a characteristic shape and range in composition, composed of unconsolidated earthy, organic materials, artificial materials, or rock, that is the direct result of human manipulation or activities; can be either constructional (e.g., artificial levee) or destructional (e.g., quarry). SW anthroscape – A human-modified “landscape” of substantial and permanent alterations (removal, additions, or reorganization) of the physical shape and /or internal stratigraphy of the land, associated with management for habitation, commerce, food or fiber production, recreation, or other human activities that have substantively altered water flow and sediment transport across or within the regolith. SW anticline – (a) [landform] A unit of folded strata that is convex upward and whose core contains the stratigraphically oldest rocks, and occurs at the earth’s surface. In a single anticline, beds forming the opposing limbs of the fold dip away from its axial plane. Compare – monocline, syncline, fold. SW & HP. (b) [structural geology] A fold, at any depth, generally convex upward whose core contains the stratigraphically older rocks. GG badlands – A landscape which is intricately dissected and characterized by a very fine drainage network with high drainage densities and short, steep slopes with narrow interfluves. Badlands develop on surfaces with little or no vegetative cover, overlying unconsolidated or poorly cemented materials (clays, silts, or in some cases sandstones) sometimes with soluble minerals such as gypsum or halite. GG bajada – (colloquial: southwestern USA) A broad, gently inclined, alluvial piedmont slope extending from the base of a mountain range out into a basin and formed by the lateral coalescence of a series of alluvial fans. Typically it has a broadly undulating transverse profile, parallel to the mountain front, resulting from the convexities of component fans. The term is generally restricted to constructional slopes of intermontane basins. Synonym – coalescent fan piedmont. Compare – fan apron. HP & SW bald – (not preferred; colloquial: southeastern USA; use summit, mountaintop, etc.) An ecological term for the grass or shrub covered (naturally tree-less) summit of a high elevation hill or mountain, flanked by forested slopes; not above the local tree-line. Compare – glade. SW & GG ballena – (colloquial: western USA) A fan remnant having a distinctively-rounded surface of fan alluvium. The ballena's broadly-rounded shoulders meet from either side to form a narrow summit and merge smoothly with concave side slopes and then concave, short pediments which form smoothly-rounded drainageways between adjacent ballenas. A partial ballena is a fan remnant large enough to retain some relict fan surface on a remnant summit. Compare – fan remnant. SW & FFP ballon – (colloquial: western USA) A rounded, dome-shaped hill, formed either by erosion or uplift. GG bar – (a) [streams] A general landform term for a ridge-like accumulation of sand, gravel, or other alluvial material formed in the channel, along the banks, or at the mouth of a stream where a decrease in velocity induces deposition; e.g., a channel bar or a meander bar. (b) [coast] A generic landform term for any of various elongate offshore ridges, banks, or mounds of sand, gravel, or other unconsolidated material submerged at least at high tide, and built up by the action of waves or currents, especially at the mouth of a river or estuary, or at a slight distance offshore from the beach. Compare – longshore bar. GG & GSST bar – [microfeature term] A small, sinuous or arcuate, ridge-like lineation on a flood plain and separated from others by small channels or troughs; caused by fluvial processes and common to flood plains and young alluvial terraces; a constituent part of bar and channel topography. Compare – meander scroll. SW bar and channel topography – A local-scale topographic pattern of recurring, small, sinuous or arcuate ridges separated by shallow troughs irregularly spaced across low-relief flood plains(slopes generally 2 –6 %); the effect is one of a subdued, sinuously undulating surface that is common on active, meandering flood plains. Micro- elevational differences between bars and channels generally range from <0.5 to 2 m and are largely controlled by the competency of the stream. The ridge-like bars often consist of somewhat coarser sediments compared to the finer textured sediments of the micro-low troughs. Compare – meander scroll, meander belt. SW barchan dune – A crescent-shaped dune with tips extending leeward (downwind), making this side concave and the windward (upwind) side convex. Barchan dunes tend to be arranged in chains extending in the dominant wind direction. Compare – parabolic dune. HP barrier bar – (not recommended) use longshore bar. barrier beach – A narrow, elongate, coarse-textured, intertidal, sloping landform that is generally parallel with the beach ridge component of a barrier island or spit and adjacent to the ocean. Compare – barrier island. SSS barrier beach [relict] – (colloquial: western USA) A wide, gently-sloping portion of a bolson floor comprising numerous, parallel, closely-spaced, relict longshore bars and lagoons built by a receding pluvial lake. Synonym, offshore barrier, offshore beach, bar beach. Compare – bar – [coast], barrier island. GG and FFP barrier cove – A subaqueous area adjacent to a barrier island or submerged barrier beach that forms a minor embayment or cove within the larger basin. Compare – cove, mainland cove. SSS barrier flat – A relatively flat, low-lying area, commonly including pools of water, separating the exposed or seaward edge of a barrier beach or barrier island from the lagoon behind it. An assemblage of both deflation flats left behind migrating dunes and /or storm washover sediments; may be either barren or vegetated. Compare – barrier beach, back-barrier flat. SSS barrier island – A long, narrow, sandy island, that is above high tide and parallel to the shore that commonly has dunes, vegetated zones, and swampy or marshy terrains extending lagoonward from the beach. Compare – barrier beach. GG barrow pit – (not preferred) refer to borrow pit. basal till – (not preferred) refer to subglacial till. base level – The theoretical limit or lowest level toward which erosion of the Earth's surface constantly progresses but seldom, if ever, reaches; especially the level below which a stream cannot erode its bed. The general or ultimate base level for the land surface is sea level, but temporary base levels commonly exist locally. GG base slope – [geomorphology] A geomorphic component of hills consisting of the concave to linear slope (perpendicular to the contour) which, regardless of the lateral shape is an area that forms an apron or wedge at the bottom of a hillside dominated by colluvial and slope wash processes and sediments (e.g., colluvium and slope alluvium). Distal base slope sediments commonly grade to, or interfinger with, alluvial fills, or gradually thin to form pedisediment over residuum. Compare – head slope, side slope, nose slope, interfluve, free face. SW basin – (a) Drainage basin. (b) A low area in the Earth's crust, of tectonic origin, in which sediments have accumulated. GG. (c) (colloquial: western USA) A general term for the nearly level to gently sloping, bottom surface of an intermontane basin (bolson). Landforms include playas, broad alluvial flats containing ephemeral drainageways, and relict alluvial and lacustrine surfaces that rarely, if ever, are subject to flooding. Where through-drainage systems are well developed, flood plains are dominant and lake plains are absent or of limited extent. Basin floors grade mountainward to distal parts of piedmont slopes. FFP basin floor – A general term for the nearly level, lower-most part of intermontane basins (i.e., bolsons, semi- bolsons). The floor includes all of the alluvial, eolian, and erosional landforms below the piedmont slope. Compare – basin, piedmont slope. FFP basin-floor remnant – (colloquial: western USA) A relatively flat, erosional remnant of any former landform of a basin floor that has been dissected following the incision of an axial stream. FFP batholith – A large, generally discordant plutonic rock body exposed at the land surface, with an aerial extent > 40 sq. mi. (100 km2) and no known bottom (e.g., Idaho batholith). Compare – stock. SW & GG bauxite – An off-white to dark red brown weathered detritus or rock composed of aluminum oxides (mainly gibbsite with some boehmite and diaspore), iron hydroxides, silica, silt, and especially clay minerals. Bauxite originates in tropical and subtropical environments as highly weathered residue from carbonate or silicate rocks and can occur in concretionary, earthy, pisolitic, or oolitic forms. SW & GG bay [coast] – (a) A wide, curving open indentation, recess, or arm of a sea (e.g., Chesapeake Bay) or lake (e.g., Green Bay, WI) into the land or between two capes or headlands, larger than a cove [coast], and usually smaller than, but of the same general character as, a gulf. (b) A large tract of water that penetrates into the land and around which the land forms a broad curve. By international agreement a bay is a water body having a baymouth that is less than 24 nautical miles wide and an area that is equal to or greater than the area of a semicircle whose diameter is equal to the width of the bay mouth. Compare – gulf. GG bay [geom.] – (a) Any terrestrial formation resembling a bay of the sea, as a recess or extension of lowland along a river valley or within a curve in a range of hills. (b) A Carolina Bay. GG & GSST bay bottom – The nearly level or slightly undulating central portion of a submerged, low-energy, depositional estuarine embayment characterized by relatively deep water (1.0 to >2.5 m). Compare – lagoon bottom. SSS bayou – A term applied to many local water features in the lower Mississippi River basin and in the Gulf Coast region of the USA. Its general meaning is a creek or secondary watercourse that is tributary to another body of water; especially a sluggish and stagnant stream that follows a winding course through alluvial lowlands, coastal swamps or river deltas. Compare – oxbow, slough. GG beach – (a) A gently sloping zone of unconsolidated material, typically with a slightly concave profile, extending landward from the low-water line to the place where there is a definite change in material or physiographic form (such as a cliff) or to the line of permanent vegetation (usually the effective limit of the highest storm waves); a shore of a body of water, formed and washed by waves or tides, usually covered by sand or gravel. (b) the relatively thick and temporary accumulation of loose water-borne material (usually well-sorted sand and pebbles) accompanied by mud, cobbles, boulders, and smoothed rock and shell fragments, that is in active transit along, or deposited on, the shore zone between the limits of low water and high water. GG beach plain – A continuous and level or undulating area formed by closely spaced successive embankments of wave-deposited beach material added more or less uniformly to a prograding shoreline, such as to a growing compound spit or to a cuspate foreland. Compare – wave-built terrace, chenier plain. GG beach ridge – A low, essentially continuous mound of beach or beach-and-dune material heaped up by the action of waves and currents on the backshore of a beach, beyond the present limit of storm waves or the reach of ordinary tides, and occurring singly or as one of a series of approximately parallel deposits. The ridges are roughly parallel to the shoreline and represent successive positions of an advancing shoreline. GG beach sands – [soil survey] Well sorted, sand-sized, clastic material transported and deposited primarily by wave action and deposited in a shore environment. Compare – eolian sands. SW beach terrace – (a) A landform that consists of a wave-cut scarp and wave-built terrace of well-sorted sand and gravel of marine and lacustrine origin. (b) (colloquial: western USA) relict shorelines from pluvial lakes, generally restricted to valley sides. Compare – strandline, shoreline. FFP beaded drainage pattern – (not recommended) use beaded stream pattern. beaded stream pattern – A characteristic pattern of small streams in areas underlain by ice wedges. The course of the stream channel is controlled by the pattern of the wedges, with beads (pools) occurring at the junctions of the wedges. NRC bed – [stratigraphy] The layer of sediments or sedimentary rocks bounded above and below by more or less well- defined bedding surfaces. The smallest, formal lithostratigraphic unit of sedimentary rocks. The designation of a bed or a unit of beds as a formally named lithostratigraphic unit generally should be limited to certain distinctive soils with substantial amounts of smectite clay minerals (e.g., Vertisols). Bowl morphology is distinct from that in adjacent microslopes (intermediate position) and microhighs (chimney). Substratum morphology is not preserved within the bowl. Compare – chimney, intermediate position, gilgai. SW box canyon – (a) A narrow gorge or canyon containing an intermittent stream following a zigzag course, characterized by high, steep rock walls and typically closed upstream by a similar wall, giving the impression, as viewed from its bottom, of being surrounded or “boxed in” by almost vertical walls. (b) A steep-walled canyon heading against a cliff a dead-end canyon. GG braided channel – (not recommended) use braided stream. braided stream – A channel or stream with multiple channels that interweave as a result of repeated bifurcation and convergence of flow around inter-channel bars, resembling (in plan view) the strands of a complex braid. Braiding is generally confined to broad, shallow streams of low sinuosity, high bed load, non-cohesive bank material, and a steep gradient. At a given bank-full discharge, braided streams have steeper slopes and shallower, broader, and less stable channel cross sections than meandering streams. Compare – meandering channel, flood- plain landforms. HP breached anticline – A structurally-controlled landscape or landform typically underlain by sedimentary rocks in which an anticline crest has been eroded such that the former crest has become a canyon or valley flanked by inward-facing erosional scarp slopes or cliffs and outward-facing dip slopes. When used as a landscape term, the associated landforms include cuestas and strike valleys. SW & GG break – (a) [slopes] An abrupt change or inflection in a slope or profile (as in “a break in slope”). Compare – knickpoint, shoulder, escarpment. (b) [geomorphology] A marked variation of topography, or a tract of land distinct from adjacent land, or an irregular or rough piece of ground. Compare – breaks. GG breaks – (colloquial: western USA) A landscape or large tract of steep, rough or broken land dissected by ravines and gullies and marks a sudden change in topography as from an elevated plain to lower hilly terrain, or a line of irregular cliffs at the edge of a mesa or a river (e.g., the Missouri River breaks). SW & GG breaklands – An assemblage of very steep (e.g. 60-90 %), high relief slopes flanking major rivers and streams in mountainous terrain that form the walls of a v-shaped river valley. Breaklands are characterized by colluviated slopes of which the majority of the ground surface drains directly to a large axial stream at the base, and the remainder consists of shallowly incised, parallel drainageways. Breaklands have shallow to very deep soils, substantial rock outcrop, and more frequent fires than lower-gradient mountain slopes above; extensive along the rivers and streams of the Idaho Batholith. Compare – dissected breaklands. SW & HD breccia – A coarse-grained, clastic rock composed of angular rock fragments (larger than 2 mm) commonly bonded by a mineral cement in a finer-grained matrix of varying composition and origin. The consolidated equivalent of rubble. Compare – conglomerate. GSST broad interstream divide – (colloquial: southeastern USA) A type of very wide, low gradient (level to nearly level) interfluve that lacks a well developed drainage network such that large portions of the local upland lack stream channels or other drainageways; extensive in lower coastal plains and some lake plains, till plains and alluvial plain remnants. Compare – interfluve. SW & RD brook – [streams] (not preferred: refer to ephemeral stream) Generally a very small, ephemeral stream, especially one that issues from a spring or seep and conducts less water volume and over shorter distances than a creek. Compare – intermittent stream. GG burial mound – A pile, hillock, or human-made hill, composed of debris or earth heaped up to mark a burial site. ICOMANTH & GG buried – (adjective) Landforms, geomorphic surfaces, or paleosols covered by younger sediments (e.g., eolian, glacial, and alluvial). Compare – exhumed, relict. HP buried soil – Soil covered by an surface mantle of new soil material, typically to depths exceeding 50 cm; recent surface deposits < 50 cm thick are generally considered as part of the ground soil. Compare – ground soil, exhumed, relict. GSST & ST butte – An isolated, generally flat-topped hill or mountain with relatively steep slopes and talus or precipitous cliffs and characterized by summit width that is less than the height of bounding escarpments, commonly topped by a caprock of resistant material and representing an erosion remnant carved from flat-lying rocks. Compare – mesa, plateau, cuesta. HP & GG caldera – A large, more or less circular depression, formed by explosion and/or collapse, which surrounds a volcanic vent or vents, and whose diameter is many times greater than that of the included vent, or vents. Compare – volcanic crater. GG caliche – A general term for a prominent zone of secondary carbonate accumulation in surficial materials in warm, subhumid to arid areas. Caliche is formed by both geologic and pedologic processes. Finely crystalline calcium carbonate forms a nearly continuous surface-coating and void-filling medium in geologic (parent) materials. Cementation ranges from weak in non-indurated forms to very strong in types that are indurated. Other minerals (carbonates, silicates, sulfates) may be present as accessory cements. Most petrocalcic and some calcic horizons are caliche. HP canyon – A long, deep, narrow, very steep–sided valley cut primarily in bedrock with high and precipitous walls in an area of high local relief (e.g., mountain or high plateau terrain), often with a perennial stream at the bottom; similar to but larger than a gorge. Compare – gorge, box canyon, slot canyon. SW, HP, & GG canyon bench – One of a series of relatively narrow, flat landforms occurring along a canyon wall and caused by differential erosion of alternating strong and weak horizontal strata; a type of structural bench. SW & GG canyon wall – The steep to near vertical slope between a canyon bottom and higher, adjacent hillslopes, mountain slopes, or summits. Canyon walls are generally dominated by rock outcrop and/or bedrock within the soil profile. Canyon walls commonly include cliffs or ledges, and may include a beveled base cut into less resistant rocks (e.g., shale). In large canyons (e.g., Grand Canyon), canyon walls may be vertically interrupted by nearly level or gentle slopes of canyon benches. SW canyonlands – A deeply and extensively dissected landscape composed predominantly of relatively narrow, steep-walled valleys with small flood plains or valley floors; commonly with considerable outcrops of hard bedrock on steep slopes, ledges, or cliffs, and with broader summits or interfluves than found in badlands. Side slopes exhibit extensive erosion, active back-wearing, and relatively sparse vegetation. SW caprock – (a) A hard rock layer, usually sandstone, lava, or in arid environments, limestone, that lies above shale or other less resistant bedrock or sediments; specifically a rock layer that forms relatively level, resistant topmost strata that holds up hills, ridges, mesas, etc., and commonly forms cliffs or escarpments. Also spelled “cap rock”. SW & GG. (b) A hard rock layer, usually sandstone, overlying the shale above a coal bed. Also spelled “cap rock”. GG captured stream – A stream whose course has been diverted into the channel of another stream by natural processes. GG Carolina Bay – Any of various shallow, often oval or elliptical, generally marshy, closed depressions in the Atlantic coastal plain (from southern New Jersey to northeastern Florida, especially developed in the Carolinas) which share an approximately parallel orientation of their long axes. They range from about 100 meters to many kilometers in length, are rich in humus, and under native conditions contain trees and shrubs different from those of the surrounding areas. Also called Grady ponds (colloquial: Georgia and Alabama) and Delmarva Bays (colloquial: Maryland). Compare – pocosin. GG cat clay – (not recommended: obsolete) Wet, clay-dominated soils containing ferrous sulfide which become highly acidic when drained. GSST catena – (as used in USA) A sequence of soils across a landscape, of about the same age, derived from similar parent material, and occurring under similar climatic conditions, but have different characteristics due to variations in relief and in drainage. GSST catsteps – (not preferred: refer to terracettes) A terracette; especially one produced by slumping of loess deposits as in western Iowa. GG centripetal drainage pattern – A drainage pattern in which the streams converge inward toward a central depression; generally indicative of a structural basin, volcanic crater, caldera, breached dome, bolson, or the end of an eroded anticline or syncline. SW, GG, & WA channel – (a) [streams] The hollow bed where a natural body of surface water flows or may flow. The deepest or central part of the bed of a stream, containing the main current and occupied more or less continuously by water. (b) (colloquial: western USA) The bed of a single or braided watercourse that commonly is barren of vegetation and is formed of modern alluvium. Channels may be enclosed by banks or splayed across and slightly mounded above a fan surface and include bars and mounds of cobbles and stones. (c) [microfeature term] Small, trough- like, arcuate or sinuous channels separated by small bars or ridges, caused by fluvial processes; common to flood plains and young alluvial terraces; a constituent part of bar and channel topography. GG, FFP, & SW chenier – A long, narrow, vegetated marine beach ridge or sandy hummock, 1 to 6 m high, forming roughly parallel to a prograding shoreline seaward of marsh and mud-flat deposits, enclosed on the seaward side by fine- grained sediments, and resting on foreshore or mud-flat deposits. It is well drained, often supporting trees on higher areas. Widths range from 45 - 450 m and lengths may exceed several tens of kilometers. GG chenier plain – A mud-rich strand plain, occupied by cheniers and intervening mud flats with marsh and swamp vegetation. Compare – chenier, strand plain. GG chert – A hard, extremely dense or compact, dull to semivitreous, cryptocrystalline sedimentary rock, consisting dominantly of interlocking crystals of quartz less than about 30 mm in diameter; it may contain amorphous silica (opal). It sometimes contains impurities such as calcite, iron oxide, or the remains of siliceous and other organisms. It has a tough, splintery to conchoidal fracture and may be white or variously colored gray, green, blue, pink, red, yellow, brown, and black. Chert occurs principally as nodular or concretionary segregations in limestones and dolomites. GG chimney – [gilgai] A subsurface morphology that forms a crude cone or wave-crest structure centered under a microhigh (e.g., a low mound or rim) and extends at least part-way under adjacent intermediate positions; composed of substratum material that appears to upwell and reaches close to the surface. A chimney is commonly bounded by master slickensides in the subsoil with maximum angles of dip reaching 60 - 75 degrees under the microhigh. Its morphology is distinct from the solum of the adjacent microslopes and microlows (e.g., lighter colored, more alkaline, and contains carbonate or gypsum concretions absent under microslopes and microlows). Compare – puff, bowl, intermediate position, gilgai. SW collapsed outwash plain – An outwash plain which forms on glacial ice (inside the glacial margin), and is subsequently let down or collapsed when the underlying ice melts, resulting in contortion or folding of the sediments and sedimentary structures to the extent that little of the original plain or its gradient remain. Outwash sediments commonly cap present-day topography. Compare – collapsed lake plain, pitted outwash plain. SW & CF colluvial – (adjective) Pertaining to material or processes associated with transportation and/or deposition by mass movement (direct gravitational action) and local, unconcentrated runoff (overland flow) on side slopes and/or at the base of slopes. Compare – alluvial, fluvial. HP colluvial apron – A landform with a concave to planar surface composed of a thick wedge-shaped deposit of colluvium and/or slope alluvium that forms the base (footslope) of a bluff, escarpment or steep slope . Compare – beveled base. SW colluvium – Unconsolidated, unsorted earth material being transported or deposited on side slopes and/or at the base of slopes by mass movement (e.g., direct gravitational action) and by local, unconcentrated runoff. Compare – alluvium, slope alluvium, scree, talus, mass movement. HP competence – The ability of a current of water or wind to transport sediment, in terms of particle size rather than amount, measured as the diameter of the largest particle transported. It depends upon velocity: a small but swift current for example, may have greater competence than a larger but slower moving current. GG complex landslide – A category of mass movement processes, associated sediments (complex landslide deposit), or resultant landforms characterized by a composite of several mass movement processes none of which dominates or leaves a prevailing landform. Numerous types of complex landslides can be specified by naming the constituent processes evident (e.g., a complex earth spread – earthflow landslide). Compare – fall, topple, slide, lateral spread, flow, landslide. SW & DV composite cone – (not preferred) see stratovolcano. compound sinkhole – (not preferred) refer to karst valley. cone karst – A variety of kegel karst topography, common in the tropics (e.g., Puerto Rico, Pacific Basin Islands) characterized by steep-sided, cone-shaped residual hills and ridges separated by star-shaped depressions, broader valleys, or lagoons. These hills and ridges have steep, convex side slopes and rounded tops that are dissected into secondary karst surfaces with shafts and various forms of karren microfeatures. Compare – karst cone, cockpit karst, fluviokarst, sinkhole karst, tower karst. SW, GG, & WW conformity – The mutual and undisturbed relationship between adjacent sedimentary strata that have been deposited in orderly sequence with little or no evidence of time lapses; true stratigraphic continuity in the sequence of beds without evidence that the lower beds were folded, tilted, or eroded before the higher beds were deposited. Compare – unconformity. GG congelifraction – (not preferred) refer to frost shattering. congeliturbate – (not recommended) use cryoturbate. congeliturbation – (not recommended) use cryoturbation. conglomerate – A coarse-grained, clastic sedimentary rock composed of rounded to subangular rock fragments larger than 2 mm, commonly with a matrix of sand and finer material; cements include silica, calcium carbonate, and iron oxides. The consolidated equivalent of gravel. Compare – breccia. HP conservation terrace – An earthen embankment constructed across a slope for conducting water from above at a regulated flow to prevent accelerated erosion and to conserve water. Compare – hillslope terrace. SW & GSST constructional – [geomorphology] (adjective) Said of a landform that owes its origin, form, position, or general character to depositional (aggradational) processes, such as the accumulation of sediment (e.g., alluvial fan, volcanic cone). Compare – aggradation, destructional, erosional. GG continuous permafrost – Permafrost occurring everywhere beneath the exposed land surface throughout a geographic region. Compare – discontinuous permafrost, sporadic permafrost. NRC continental glacier – A glacier of considerable thickness completely covering a large part of a continent or an area of at least 50,000 square km, obscuring the underlying surface, such as the ice sheets covering Antarctica or Greenland. Continental glaciers occupied northern portions of the coterminous USA and Alaska in the past (e.g., Pleistocene) and usage commonly implies former continental glacier conditions. Compare – alpine glacier. SW & GG coppice mound – (also called coppice dune) (not recommended: obsolete) use shrub-coppice dune. coprogenous earth – [Soil Taxonomy] A type of sedimentary peat which is a limnic layer composed predominantly of fecal material derived from aquatic animals. ST coprogenic material – [soil survey] The remains of fish excreta and similar materials that occur in some organic soils. GSST coral island – (a) A relict coral reef that stands above sea level and surrounded by water (e.g., Florida Keys). Carbonate sands rich in coral and shell fragments generally mantle the underlying flat coral platform. (b) An oceanic island formed from coral accumulations lying atop or fringing volcanic peaks or platforms. SW & GG coral limestone – An informal term for massive limestone composed primarily of coral and coral fragments commonly associated with marine islands or coral reefs in tropical or subtropical waters. Compare – coral island. SW corda – Small, tightly bunched, parallel ridges or corrugations of lava, commonly < 1 m in amplitude (high) and < 3 m in period (wide) on the surface of corded pahoehoe lava (ropy lava). SW & GS corrosion – [geomorphology] A process of erosion whereby rocks and soil are removed or worn away by natural chemical processes, especially by the solvent action of running water, but also by other reactions, such as hydrolysis, hydration, carbonation, and oxidation. GG coulee – (colloquial: northwestern USA and ND) A dry or intermittent stream valley or wash with an underfit stream, especially a long, steep-walled gorge representing a Pleistocene overflow channel that carried meltwater from an ice sheet; e.g., the Grand Coulee in Washington State. HP country rock – A general term for the non-igneous rock surrounding an igneous intrusion. GG cove – [geomorphology] (a) A walled and rounded or cirque-like opening at the head of a small steep valley. (b) (colloquial: southern Appalachians, USA) A smooth-floored, somewhat oval-shaped "valley" sheltered by hills or mountains; e.g., Cades Cove in eastern Tennessee. GG cove [water] – (a) A small, narrow sheltered bay, inlet, creek or recess in an estuary, often inside a larger embayment. Compare – lagoon bottom. SSS & GG. (b) A small, often circular, wave-cut indentation in a cliff; it usually has a restricted or narrow entrance. (c) A fairly broad, looped embayment in a lake shoreline. (d) A shallow tidal river, or the backwater near the mouth of a tidal river. Compare – estuary. GG cradle and knoll topography – (not recommended) use tree-tip pit and mound topography. crag and tail – An elongate hill or ridge of subglacially streamlined drift, having at the stoss end (up-ice) a steep, often precipitous face or knob of ice-smoothed, resistant bedrock (the “crag”) obstructing the movement of the glacier, and at the lee end (down-ice) a tapering, streamlined, gentle slope (the “tail”) of intact, weaker rock and / or drift protected by the crag; also called lee-side cone. Compare – drumlin, drumlinoid ridge, flute, stoss and lee. GG, SW, & GM crater [volcanic] – see volcanic crater. craton – A part of the earth's crust that has attained stability, and has been minimally deformed for a prolonged period. The term is now restricted to continental areas of largely Precambrian rocks. GG creek – [streams] (not preferred: refer to intermittent stream) A general term used throughout the USA (except New England), Canada, and Australia for a small, intermittent stream that is larger than a brook but smaller than a river. GG creep – The mass movement process, surficial sediments (creep deposit), or landform that results from very slow downslope mass wasting of unconsolidated earthy material driven primarily by gravity, but facilitated by water saturation and by and freeze-thaw. Sometimes redundantly called soil creep. Compare – mudflow, flow, landslide, solifluction. SW crest – (a) The commonly linear, narrow top of a ridge, hill, or mountain. It is appropriately applied to elevated areas where retreating backslopes are converging such that these high areas are almost exclusively composed of convex shoulders. (b) (not preferred) Sometimes used as an alternative for the hillslope component summit. Compare – summit (part b), saddle. FFP & SW crest – [geomorphology] A geomorphic component of hills consisting of the convex slopes (perpendicular to the contour) that form the narrow, roughly linear top area of a hill, ridge, or other upland where shoulders have converged to the extent that little or no summit remains; dominated by erosion, slope wash and mass movement processes and sediments (e.g., slope alluvium, creep). Commonly, soils on crests are more similar to those on side slopes than to soils on adjacent interfluves. Compare – interfluve, head slope, side slope, nose slope. SW crevasse – [geomorphology] (a) A wide breach or crack in the bank of a river or canal; especially one in a natural levee or an artificial bank of the lower Mississippi River. Compare – avulsion, flood-plain splay. (b) A wide, deep break or fissure in the Earth after an earthquake. [glaciology] A deep, nearly vertical fissure, crack, or rift in a glacier or other mass of land ice. GG crevasse filling – A short, straight ridge of stratified sand and gravel believed to have been deposited in a crevasse of a wasting glacier and left standing after the ice melted; a variety of kame. May also occur as long, sinuous ridges and linear complexes of till or drift. GG crevasse splay – (not recommended) use flood-plain splay. Compare – crevasse. cross-bedding – (a) Cross-stratification in which the cross-beds are more than 1 cm in thickness. (b) A cross- bedded structure; a cross-bed. Compare – cross-lamination. GG cross-lamination – (a) Cross-stratification characterized by cross-beds that are less than 1 cm in thickness. (b) A cross-laminated structure; a cross-lamina. Compare – cross-bedding. GG deflation – The sorting out, lifting and removal of loose, dry, fine-grained soil particles (clays, silts, and fine sands) by the turbulent eddy action of the wind; a form of wind erosion. GG & GSST deflation basin – A topographic basin excavated and maintained by wind erosion which removes unconsolidated material and commonly leaves a rim of resistant material surrounding the depression. Unlike a blowout, a deflation basin does not include adjacent deposits derived from the basin. Compare – blowout. GG deflation flat – (colloquial: US Gulf Coast) A series of low ridges and troughs on an essentially flat surface on barrier islands formed by dune field migration during alternating wet and dry periods; a type of interdune. Troughs are eroded down to the wet sand level during drought periods (dune slack), while the ridges are stabilized by vegetation that invades the edge of dune fields during wet periods. Compare – blowout, deflation basin. HF degradation – [geomorphology] The wearing down or away, and the general lowering of the land surface by natural processes of weathering and erosion (e.g., the deepening by a stream of its channel) and may infer the process of transportation of sediment. Compare – destructional. GG Delmarva Bay – see Carolina Bay. delta – A body of alluvium, nearly flat and fan-shaped, deposited at or near the mouth of a river or stream where it enters a body of relatively quiet water, usually a sea or lake. HP delta plain – The level or nearly level surface composing the land-ward part of a large delta; strictly, a flood plain characterized by repeated channel bifurcation and divergence, multiple distributary channels, and interdistributary flood basins. GG dendritic drainage pattern – A common drainage pattern in which the tributaries join the gently curving mainstream at acute angles, resembling in plan view the branching habit of an oak or chestnut tree; it is produced where a consequent stream receives several tributaries which in turn are fed by smaller tributaries. It indicates streams flowing across horizontal rock strata and homogenous soil typified by the landforms of soft sedimentary rocks, volcanic tuff, old dissected coastal plains, or complex crystalline rocks offering uniform resistance to erosion. SW, WA, GG deposit – Either consolidated or unconsolidated material of any type that has accumulated by natural processes or by human activity. SW deposition – The laying down of any material by any agent such as wind, water, ice or by other natural processes. HP depression – Any relatively sunken part of the Earth's surface; especially a low-lying area surrounded by higher ground. A closed depression has no natural outlet for surface drainage (e.g., a sinkhole). An open depression has a natural outlet for surface drainage. Compare – closed depression, open depression. GG deranged drainage pattern – A distinctively disordered drainage pattern of nonintegrated streams which indicates a complete lack of underlying structural and bedrock control, resulting from a relatively young landscape having a flat or undulating topographic surface and a high water table. It is characterized by relatively few, irregular streams with few, short tributaries, that flow into and out of depressions containing swamps, bogs, marshes, ponds, or lakes; interstream areas are swampy. Regional streams may meander through the area but do not influence its drainage. These drainage patterns commonly occur on young, thick till plains, end moraines, flood plains, and coastal plains. SW & WA desert pavement – A natural, residual concentration or layer of wind-polished, closely packed gravel, boulders, and other rock fragments, mantling a desert surface. It is formed where wind action and sheetwash have removed all smaller particles or where rock fragments have migrated upward through sediments to the surface. It usually protects the underlying, finer-grained material from further deflation. Compare – erosion pavement, stone line. SW, GSST, & GG desert varnish – (not preferred) refer to rock varnish. destructional – [geomorphology] (adjective) Said of a landform that owes its origin, form, position, or general character to the removal of material by erosion and weathering (degradation) processes resulting from the wearing-down or away of the land surface. Compare – constructional. GG detritus – [geology] A collective term for rock and mineral fragments occurring in sediments, that are detached or removed by mechanical means (e.g., disintegration, abrasion) and derived from pre-existing rocks and moved from their place of origin. Compare – clastic, epiclastic, pyroclastic. GG diamict – (not preferred; refer to diamicton) A general term that includes both diamictite (coherent rock) and diamicton (unconsolidated sediments). GG diamictite – A general term for any nonsorted or poorly sorted, noncalcareous, terrigenous sedimentary rock (e.g., pebbly mudstone) containing a wide range of particle sizes. Compare – diamicton. GG diamicton – A generic term for any nonlithified, nonsorted or poorly sorted sediment that contains a wide range of particle sizes, such as rock fragments contained within a fine earth matrix (e.g., till) and used when the genetic context of the sediment is uncertain. Compare – diamictite. SW & GG diapir – A dome or anticlinal fold in which the overlying rocks or sediments have been ruptured by the squeezing-out of plastic core material. Diapirs in sedimentary strata usually contain cores of salt or shale; igneous intrusions may also show diapiric structure. GG diatomaceous earth – [geology] A lacustrine or marine geologic deposit of fine, grayish, siliceous material composed chiefly or wholly of the remains of diatoms. It may occur as a powder or a rigid material (i.e., diatomite). GSST diatomaceous earth – [Soil Taxonomy] A layer of soil material (limnic materials) that is composed of diatoms. Diatomaceous earth is identified by several diagnostic criteria such as moist color value which changes on drying as a result of the irreversible shrinkage of organic-matter coats on diatoms and either a moist color value of 8 or more and a chroma of 2 or less from a saturated sodium-pyrophosphate extract on white chromatographic or filter paper, or a cation-exchange capacity of less than 240 cmol (+) per kg organic matter (measured by loss on ignition). KST & ST diatomite – A light-colored, soft, siliceous sedimentary rock consisting chiefly of opaline diatom frustules deposited in a lacustrine or marine environment. Diatomite has a number of uses owing to its high surface area, absorptive capacity, and relative chemical stability but the term is generally reserved for deposits of actual or potential commercial value. Compare – diatomaceous earth – (geology). GG diatreme – A breccia-filled volcanic pipe that was formed by a gaseous explosion (e.g., hydrovolcanic eruption); commonly, but not exclusively associated with exposed throat or neck of maar, as in the Hopi Buttes area of northeastern Arizona. Compare – volcanic neck. SW & GG dike – [intrusive rocks] A tabular igneous intrusion that cuts across the bedding or foliation of the country rock. Compare – sill. GG dip – [soil survey] A geomorphic component (characteristic piece) of flat plains (e.g., lake plain, low coastal plain, low-relief till plain) consisting of a shallow and typically closed depression that tends to be an area of focused groundwater recharge but not a permanent water body and that lies slightly lower and is wetter than the adjacent talf, and favors the accumulation of fine sediments and organic materials. SW dip – [structural geology] The maximum angle that a structural surface, (e.g., a bedding or fault plane) makes with the horizontal, measured perpendicular to the strike of the structure and in the vertical plane; used in combination with “dip” to describe the orientation of bedrock strata. SW & GG dip slope – A slope of the land surface, roughly determined by and approximately conforming to the dip of underlying bedded rocks; (i.e., the long, gently inclined surface of a cuesta). Compare – scarp slope. HP discontinuity – [stratigraphy] Any interruption in sedimentation, whatever its cause or length, usually a manifestation of nondeposition and accompanying erosion; an unconformity. GG discontinuous permafrost – Permafrost occurring in some areas beneath the exposed land surface throughout a geographic region where other areas are free of permafrost. Compare – continuous permafrost, sporadic permafrost. NRC disintegration moraine – A drift topography characterized by chaotic mounds and pits, generally randomly oriented, developed in supraglacial drift by collapse and flow as the underlying stagnant ice melted. Slopes may be steep and unstable and there will be used and unused stream courses and lake depressions interspersed with the morainic ridges. Characteristically, there are numerous abrupt, lateral and vertical changes between unconsolidated materials of differing lithology. SJ & SW dissected breaklands – Very steep slopes flanking major rivers and streams in mountainous terrain and dominated by deeply incised, sub-parallel to dendritic, chute-like drainageways that occupy > 50 % of the ground surface. Dissected breakland slopes are dominated by hillslope elements that grade to secondary drainageways, rather than directly to the axial stream; a type of breakland. SW & HD dissected plateau – A land area (landscape) produced by significant stream erosion and incision of a plateau such that only a small part of the plateau surface is at or near the original summit level. Much of the area occurs as hillslopes, or if incision is sufficient and relief is > 1000 feet, as mountain slopes. Compare – plateau. SW distal – (sedimentology; adjective) Said of a sedimentary deposit consisting of fine clastics and deposited farthest from the source area. Compare – proximal. GG distributary – [streams] (a) A divergent stream flowing away from the main stream and not returning to it, as in a delta or on a flood plain. It may be produced by stream deposition choking the original channel. (b) One of the channels of a braided stream; a channel carrying the water of a stream distributary. GG ditch – An open and usually unpaved (unlined), channel or trench excavated to convey water for drainage (removal) or irrigation (addition) to or from a landscape; smaller than a canal; some ditches are modified natural waterways. GG divide – A summit area or tract of high ground, which can vary from broad to narrow, or a line of separation that constitutes a watershed boundary between adjacent drainage basins; a divide separates surface waters that flow naturally in one direction from those that flow in a different or opposite direction. Compare – interfluve. GG doline – (not preferred) refer to synonym “sinkhole”. dune slack – A damp depression or trough between dunes in a dune field or dune ridges on a shore, caused by intersecting the capillary fringe of the local water table; a moist type of interdune. Compare – interdune, dune lake. SW & GG dune traces – A series of linear to semi-concentric micro-ridges and intervening troughs, on the floor of a dune slack or interdune that were exposed by deflation or dune migration. The ridges are remnant bases of slip face lamina held together by soil moisture and /or cemented by evaporites. SW earth dike – (not preferred) refer to levee. earth fall – see soil fall. earth hummock – A type of hummock consisting predominantly of a core of silty and clayey mineral soil and showing evidence of cryoturbation. Earth hummocks are a type of nonsorted circle. Compare – turf hummock, hummock [patterned ground], nonsorted circle, patterned ground. NRC earth pillar – A tall, conical column of unconsolidated to semi-consolidated earth materials (e.g., clay till, or landslide debris) produced by differential erosion and usually capped by a flat, hard rock fragment that shields the underlying, softer material from erosion. It can measure up to 6-20 m in height, and its diameter is a function of the width of the protective boulder. Compare – hoodoo. GG earth spread – The mass movement process, associated sediments (earth spread deposit), or resultant landform characterized by a very rapid type of spread dominated by lateral movement in a soil mass resulting from liquefaction or plastic flow of underlying materials that may be extruded out between intact units. Compare – debris spread, rock spread, landslide. SW & DV earth topple – The mass movement process, associated sediments (earth topple deposit), or resultant landform characterized by a localized, very rapid type of topple in which large blocks of soil material literally fall over, rotating outward over a low pivot point; sediments < 2 mm predominate. Portions of the original material may remain intact, although reoriented, within the resulting deposit. Compare –debris topple, rock topple, landslide. SW earthflow – The mass movement process, associated sediments (earthflow deposit), or resultant landform characterized by slow to rapid flow dominated by downslope movement of soil, rock, and mud (more than 50% of the particles are < 2 mm), and whether saturated or comparatively dry, behaves as a viscous fluid when moving. Compare – debris flow (coarser, less fluid), mudflow (finer, more fluid). SW elevation – [survey] The height of a point on the earth’s surface relative to mean sea level (msl). Compare – relief. SW elevated lake plain – (not preferred) refer to collapsed lake plain, collapsed ice-floored lakebed. elliptical gilgai – A type of gilgai dominated by elliptical, closed and semi-closed depressions (microlows) separated by low mounds or ridges (microhighs); the prevailing type of gilgai on mildly sloping terrain (slopes 3 – 8 %); as slope increases, basins become more eccentric and the occurrence of interconnected micro-lows increases. Compare – circular gilgai, linear gilgai, gilgai. SW end moraine – A ridge-like accumulation that is being or was produced at the outer margin of an actively flowing glacier at any given time; a moraine that has been deposited at the outer or lower end of a valley glacier. Compare – terminal moraine, recessional moraine, ground moraine. GG Eocene – An epoch (from 35.4 to 56.5 million years ago) of the Tertiary Period of geologic time that follows the Paleocene and precedes the Oligocene epoch; also the corresponding (time-stratigraphic) “series” of earth materials. SW eolian – Pertaining to material transported and deposited (eolian deposit) by the wind. Includes clastic materials such as dune sands, sand sheets, loess deposits, and clay (e.g., parna). HP eolian deposit – [soil survey] Sand, silt or clay-sized clastic material transported and deposited primarily by wind, commonly in the form of a dune or a sheet of sand or loess. Conventionally, primary volcanic deposits (e.g., tephra) are handled separately. Compare – loess, parna, beach sands. SW eolian sands – [soil survey] Sand-sized, clastic material transported and deposited primarily by wind, commonly in the form of a dune or a sand sheet. Compare – beach sands. SW ephemeral stream – Generally a small stream, or upper reach of a stream, that flows only in direct response to precipitation. It receives no protracted water supply from melting snow or other sources and its channel is above the water table at all times. Compare – arroyo, intermittent stream, perennial stream. HP epiclastic – (adjective) Pertaining to any clastic rock or sediment other than pyroclastic. Constituent fragments are derived by weathering and erosion rather than by direct volcanic processes. Compare – pyroclastic, volcaniclastic, clastic, detritus. HP eroded fan remnant – All, or a portion of an alluvial fan that is much more extensively eroded and dissected than a fan remnant; sometimes called an erosional fan remnant (FFP). It consists primarily of a) eroded and highly dissected sides (eroded fan-remnant sideslopes) dominated by hillslope positions (shoulder, backslope, etc.), and b) to a lesser extent an intact, relatively planar, relict alluvial fan “summit” area best described as a tread. SW & FFP eroded fan-remnant sideslope – A rough or broken margin of an eroded fan remnant highly dissected by ravines and gullies that can be just a fringe or make up a large part of an eroded alluvial fan; its bounding escarpments (risers), originally formed by inset channels, have become highly dissected and irregular such that terrace components (tread and riser) have been consumed or modified and replaced by hillslope positions and components (shoulder, backslope, footslope, etc.); sometimes referred to as fan remnant sideslopes (FFP). Compare – eroded fan remnant. SW & FFP erosion – The wearing away of the land surface by running water, waves, or moving ice and wind, or by such processes as mass wasting and corrosion (solution and other chemical processes). The term "geologic erosion" refers to natural erosion processes occurring over long (geologic) time spans. "Accelerated erosion" generically refers to erosion in excess of what is presumed or estimated to be naturally occurring levels, and which is a direct result of human activities (e.g., cultivation, logging, etc.). SW & HP erosional – [geomorphology] (adjective) Owing its origin, form, position or general character to degradational processes by water, wind, ice or gravity. Compare – constructional. HP erosional outlier – (not preferred) refer to erosion remnant. erosional pavement – see erosion pavement. erosion pavement – A surficial lag concentration or layer of gravel and other rock fragments that remains on the soil surface after sheet or rill erosion or wind has removed the finer soil particles and that tends to protect the underlying soil from further erosion. Compare – desert pavement, stone line. SW, GSST, & GG erosion remnant – A topographic feature that remains or is left standing above the general land surface after erosion has reduced the surrounding area; e.g., a monadnock, a butte, or a stack. GG erosion surface – A land surface shaped by the action of erosion, especially by running water. GG erratic – A rock fragment carried by glacial ice, or by floating ice (ice-rafting), and subsequently deposited at some distance from the outcrop from which it was derived, and generally, though not necessarily, resting on bedrock or sediments of different lithology. Fragments range in size from a pebble to a house-size block. GG escarpment – A relatively continuous and steep slope or cliff produced by erosion or faulting and that topographically interrupts or breaks the general continuity of more gently sloping land surfaces . The term is most commonly applied to cliffs produced by differential erosion. Synonym: "scarp." SW & HP esker – A long, narrow, sinuous and steep-sided ridge composed of irregularly stratified sand and gravel deposited as the bed of a stream flowing in an ice tunnel within or below the ice (subglacial) or between ice walls on top of the ice of a wasting glacier, and left behind as high ground when the ice melted. Eskers range in length from less than a kilometer to more than 160 kilometers, and in height from 3 to 30 meters. Compare – kame, crevasse filling, glaciofluvial deposits, outwash. SW estuarine deposit – Fine-grained sediments (very fine sand, silt and clay) of marine and fluvial origin commonly containing decomposed organic matter, laid down in the brackish waters of an estuary; characteristically finer sediments than deltaic deposits. Compare – fluviomarine deposit, lacustrine deposit, lagoonal deposit, marine deposit, overbank deposit. GG estuarine subaqueous soils – Soils that form in sediment found in shallow-subtidal environments in protected estuarine coves, bays, inlets, and lagoons. Excluded from the definition of these soils are any areas “permanently covered by water too deep (typically greater than 2.5 m) for the growth of rooted plants.” SSS estuary – (a) A seaward end or the widened funnel-shaped tidal mouth of a river valley where fresh water comes into contact with seawater and where tidal effects are evident; e.g., a tidal river, or a partially enclosed coastal body of water where the tide meets the current of a stream. (b) A portion of an ocean or an arm of the sea affected by fresh water. (c) A drowned river mouth formed by the subsidence of land near the coast or by the drowning of the lower portion of a non-glacial valley due to the rise of sea level. Compare – lagoon. GG everglades – (colloquial: southern USA) A large expanse of marshy land, covered mostly by grasses, e.g., the Florida Everglades. GG exfoliation – The process by which concentric scales, plates, or shells of rock, from less than a centimeter to several meters in thickness, are successively spalled or stripped from the bare surface of a large rock mass. It often results in a rounded rock mass or dome-shaped hill. GG exhumed – (adjective) Formerly buried landforms, geomorphic surfaces, or paleosols that have been re-exposed by erosion of the covering mantle. Compare – relict, buried, ground soil. HP extramorainic – (not preferred) refer to extramorainal. extramorainal – (adjective) Said of deposits and phenomena occurring outside the area occupied by a glacier and its lateral and end moraines. Compare – intramorainal. GG extrusive – (adjective) Said of igneous rocks and sediments derived from deep-seated, molten matter (magma), deposited and cooled on the earth's surface (e.g., including lava flows and tephra deposits). Compare – intrusive, volcanic. HP water, or in building dams. (b) Soil or loose rock used to raise the surface level of low-lying land, such as an embankment to fill a hollow or ravine in roads construction. GG filled marshland – A subaerial soil area composed of fill materials (construction debris, dredged or pumped sandy or shell-rich sediments, etc.) deposited and smoothed to provide building sites and associated uses (e.g., lawns, driveways, parking lots). These fill materials are typically 0.5 to 3 m thick and have been deposited unconformably over natural soils. Compare – dredge spoil bank. SW finger ridge – One in a group of small, tertiary spur ridges that form crudely palmate extensions of erosional remnants along the flanks or nose of larger ridges. Compare – ballena, rib. SW first bottom – (not recommended: colloquial: Midwestern USA - use flood-plain step) An obsolete, informal term loosely applied to the lowest flood-plain steps that experience regular flooding. However, the frequency of flooding is inconsistently specified. SW fissure vent – An opening in earth’s surface of a volcanic conduit in the form of a crack or fissure rather than a localized crater; a roughly linear crack or area along which lava, generally mafic and of low viscosity, wells up to the surface, usually without any explosive activity. The results can be an extensive lava plateau (e.g., Columbia River Plateau). Compare – volcanic crater. SW & GG fjord – A long, narrow, winding, glacially eroded, U-shaped and steep-walled, generally deep inlet or arm of the sea between high rocky cliffs of slopes along a mountainous coast. Typically it has a shallow sill or threshold of solid rock or earth material submerged near its mouth and becomes deeper far inland. A fjord usually represents the seaward end of a deep, glacially excavated valley that is partially submerged by drowning after melting of the ice. GG flat – [geomorphology] (a) (adjective) Said of an area characterized by a continuous surface or stretch of land that is smooth, even, or horizontal, or nearly so, and that lacks any significant curvature, slope, elevations, or depressions. (b) (noun) An informal, generic term for a level or nearly level surface or small area of land marked by little or no local relief. Compare – mud flat. (c) (not recommended) A nearly level region that visibly displays less relief than its surroundings. GG flat – [lake] (a) (not preferred) refer to lakebed. The low-lying, exposed, flat land of a lake delta or of a lake bottom. Compare – lake plain. (b) (not preferred) The flat bottom of a desiccated lake in the arid parts of western USA. Compare – playa, pluvial lake. GG flatwoods – (colloquial: southeastern USA) Broad, low gradient (generally < 1 % slope but up to 2% near drainageways), low relief interstream areas and characterized by non-hydric, poorly drained soils (seasonal saturation or water table) at depths of 15 to 45 cm, and naturally forested by pines that dominate the Lower Coastal Plain of the southeastern US. Regional differences occur in dominant vegetation and soil material (e.g., in south Florida, soils are dominantly sandy Spodosols and the understory is dominantly saw palmetto). Hydropedologically and elevationally this landform occurs slightly above minor depressions (which have a seasonal water table at or above the surface), drainageways, and drainhead complexes, but lies below better drained and slightly higher small rises or knolls. Generally they are most extensive toward the interiors of low, broad interstream divides and away from drainageways. SW flood plain – The nearly level plain that borders a stream and is subject to inundation under flood-stage conditions unless protected artificially. It is usually a constructional landform built of sediment deposited during overflow and lateral migration of the streams. HP flood-plain landforms – A variety of constructional and erosional features produced by stream channel migration and flooding, e.g., backswamp, braided stream, flood-plain splay, meander, meander belt, meander scroll, oxbow lake, and natural levee. HP flood-plain playa – A landform consisting of very low gradient, broad, barren, axial-stream channel segments in an intermontane basin. It floods broadly and shallowly and is veneered with barren fine-textured sediment that crusts. Commonly, a flood-plain playa is segmented by transverse, narrow bands of vegetation, and it may alternate with ordinary narrow or braided channel segments. FFP flood-plain splay – A fan-shaped deposit or other outspread deposit formed where an overloaded stream breaks through a levee (natural or artificial) and deposits its material (often coarse-grained) on the flood plain. Compare – crevasse. GG flood-plain step – An essentially flat, terrace-like alluvial surface within a valley that is frequently covered by flood water from the present stream (e.g., below the 100 year flood level); any approximately horizontal surface still actively modified by fluvial scour and/or deposition (i.e., cut and fill and/or scour and fill processes). May occur individually or as a series of steps. Compare – stream terrace. SW & RR flood-tidal delta – A largely subaqueous (sometimes intertidal), crudely fan-shaped deposit of sand-sized sediment formed on the landward side of a tidal inlet (modified from Boothroyd et al., 1985; Davis, 1994; Ritter et al., 1995). Flood tides transport sediment through the tidal inlet and into the lagoon over a flood ramp where currents slow and dissipate (Davis, 1994). Generally, flood-tidal deltas along microtidal coasts are multi-lobate and unaffected by ebbing currents (modified from Davis, 1994). Compare – flood-tidal delta slope. SSS flood-tidal delta flat – The relatively flat, dominant component of the flood-tidal delta. At extreme low tide this landform may be exposed for a relatively short period (modified from Boothroyd et al., 1985). SSS flood-tidal delta slope – An extension of the flood-tidal delta that slopes toward deeper water in a lagoon or estuary, composed of flood channels, inactive lobes (areas of the flood-tidal delta that are not actively accumulating sand as a result of flood tides), and parts of the terminal lobe of the flood-tidal delta (modified from Boothroyd et al., 1985). SSS floodwall – (not recommended) use levee. floodway – (a) A large-capacity channel constructed to divert floodwaters or excess streamflow from populous, flood-prone areas, such as a bypass route bounded by levees. (b) The part of the flood plain kept clear of encumbrances and reserved for emergency diversion of floodwaters. GG floor – [geomorphology] (a) A general term for the nearly level, lower part of a basin or valley; (not preferred) refer to basin floor, valley floor. (b) The bed of any body of water; e.g., the nearly level surface beneath the water of a stream, lake, or ocean. GG flow – A category of mass movement processes, associated sediments (flow deposit) and landforms characterized by slow to very rapid downslope movement of unconsolidated material which, whether saturated or comparatively dry, behaves much as a viscous fluid as it moves. Types of flows can be specified based on the dominant particle size of sediments [i.e., debris flow (e.g., lahar), earthflow (creep, mudflow), rockfall avalanche, debris avalanche]. Compare – fall, topple, slide, lateral spread, complex landslide, landslide. SW & DV flow till – A till that may be either subglacial or supraglacial in origin. Flow till displays secondary transport, sorting, and/or fabric modification by plastic mass flow. Flow till exhibits weak stratification and sorting and may contain distorted layers indicative of lateral displacement and soft sediment deformation. The secondary flow processes obliterate most of the original fabric and clast orientations in the till. Compare – subglacial till, supraglacial till, lodgment till, melt-out till. SW & GG flute – [glacial] A lineation or streamlined furrow or ridge parallel to the direction of ice movement, formed in newly deposited till or older drift. They range in height from a few centimeters to 25 m, and in length from a few meters to 20 km. Compare – glacial groove. GG fluve – (refer to drainageway) A roughly linear or elongated depression (topographic low) of any size, along which water flows, at some time. Compare – interfluve. FFP & SW fluvial – (adjective) Of or pertaining to rivers or streams; produced by stream or river action. Compare – alluvial, colluvial. HP fluviokarst – A karst landscape dominated by both 1) karst features (deranged and subsurface drainage, blind valleys, swallow holes, large springs, closed depressions, and caves), generally limited to low-lying interfluve areas, and 2) surface drainage by large rivers, with associated fluvial features (adjacent stream terraces) and sediments (alluvium), that commonly maintain their surface courses and are fed by underground tributaries; the dominant karst in the eastern USA. Compare – sinkhole karst, pavement karst, glaciokarst, karst. SW, WW, & GG fluviomarine bottom – The nearly level or slightly undulating, relatively low-energy, depositional environment with relatively deep water (1.0 to >2.5 m) directly adjacent to an incoming stream and composed of interfingered and mixed fluvial and marine sediments (fluviomarine deposits). SSS fluviomarine deposit – Stratified materials (clay, silt, sand, or gravel) formed by both marine and fluvial processes, resulting from non-tidal sea level fluctuations, subsidence and/or stream migration (i.e., materials originally deposited in a nearshore environment and subsequently reworked by fluvial processes as sea level fell). Compare – estuarine deposit, lacustrine deposit, lagoonal deposit, marine deposit, overbank deposit. SW fluviomarine terrace – A constructional coastal strip, sloping gently seaward and/or down valley, veneered or completely composed of fluviomarine deposits (typically silt, sand, fine gravel). Compare – terrace, stream terrace, marine terrace. SW fly ash – All particulate matter that is carried in a gas stream, especially in stack gases at a coal-fired plant for the generation of electric power; also name given to sediments from the same source, stock piled in settling ponds or spoil piles. SW & GG fold – [structural geology] A curve or bend of a planar structure such as rock strata, bedding planes, foliation, or cleavage. GG fold-thrust hills – A landscape along an orogenic belt margin underlain dominantly by sedimentary rocks that have undergone intensive structural deformation via a series of sub-parallel thrust faults and associated folds. The thrust faults typically merge along a regional, subhorizontal displacement (decollement) at the basement contact. The land area displays considerable relief, characterized by cuestas, hogbacks, strike valleys, dip slopes, scarp slopes, and structurally-controlled hills; also known as an overthrust belt (e.g., the Wyoming overthrust belt). SW & GG foothills – A steeply sloping upland composed of hills with relief of 30 up to 300 meters and fringes a mountain range or high-plateau escarpment. Compare – hill, mountain, plateau. SW & HP erosional, constructional or both. The surface shape can be planar, concave, convex, or any combination of these. Compare – constructional, erosional. RR geomorphology – The science that treats the general configuration of the earth's surface; specifically the study of the classification, description, nature, origin, and development of landforms and their relationships to underlying structures, and of the history of geologic changes as recorded by these surface features. The term is especially applied to the genetic interpretation of landforms. GG geyser – A type of hot spring that intermittently erupts jets of hot water and steam, the result of ground water coming in contact with rock or steam hot enough to create steam under conditions preventing free circulation; a type of intermittent spring. Compare – mud pot, hot spring. GG geyser basin – A valley that contains numerous springs, geysers, and steam fissures fed by the same ground- water flow. GG geyser cone – A low hill or mound built up of siliceous sinter around the orifice of a geyser. GG giant ripple – A ripple that is more than 30 m in length; e.g., the jokulhlaup derived giant ripples in Camas Prairie, MT.; it usually exhibits superimposed megaripples. Compare – ripple mark. GG gilgai – A microfeature pattern of soils composed of a succession of microbasins and microknolls on level areas, or of microtroughs and microridges parallel to the slope on sloping areas, and produced by expansion / contraction and shear / thrust processes with changes in soil moisture. Found in soils containing large amounts of smectite clay minerals that swell and shrink considerably with wetting and drying. Various types of gilgai can be recognized based on the dominant shape of microhighs and microlows: circular gilgai, elliptical gilgai, and linear gilgai. Also referred to, in part or in total, as crabhole, Bay of Biscay, or hushabye in older literature. SW & GSST glacial – (adjective) (a) Of or relating to the presence and activities of ice and glaciers, as in glacial erosion. (b) Pertaining to distinctive features and materials produced by or derived from glaciers and ice sheets, as in glacial lakes. (c) Pertaining to an ice age or region of glaciation. GG glacial drainage channel – A channel formed by an ice-marginal, englacial, or subglacial stream during glaciation. GG glacial drift – (not recommended) use drift. glacial groove – A deep, wide, usually straight furrow cut in bedrock by the abrasive action of a rock fragment embedded in the bottom of a moving glacier; it is larger and deeper than a glacial striation, ranging in size from a deep scratch to a small glacial valley. Compare – flute. GG glacial lake – (a) A lake that derives much or all of its water from the melting of glacier ice, fed by meltwater, and lying outside the glacier margins (e.g., proglacial lake) or lying on a glacier (e.g., ice-walled lake, ice-floored lake) and due to differential melting. (b) A lake occupying a basin produced by glacial deposition, such as one held in by a morainal dam. (c) A lake occupying a basin produced in bedrock by glacial erosion (scouring, quarrying); e.g., cirque lake, fjord. (d) A lake occupying a basin produced by collapse of outwash material surrounding masses of stagnant ice. (e) [relict] An area formerly occupied by a glacial lake. GG glacial-marine sedimentation – The accumulation of glacially eroded, terrestrially derived sediment in the marine environment. Sediment may be introduced by fluvial transport, by ice rafting, as an ice-contact deposit, or by eolian transport. Compare – glaciomarine deposits. GG glacial outwash – (not recommended) use outwash. glacial till – (not recommended: use till). Till should only be used for describing glacial sediments, therefore "glacial till" is redundant. GM glacial-valley floor – The comparatively flat bottom of a mountain valley predominantly mantled by till but which can grade from glacial scour (scoured rock outcrop) near its head to a thick mantle of till, and ultimately merging with alluvium or colluvium further down valley. Some glacial-valley floors descend downstream in a series of scour-derived steps which may contain sequential tarn lakes (pater noster lakes); (not preferred: colloquial: western USA) sometimes called a trough bottom. SW glacial-valley wall – The comparatively steep, glacially scoured, concave sides of a u-shaped, mountain valley mantled by colluvium with little or no till; (not preferred: colloquial: western USA) sometimes called a trough wall. SW glaciation – The formation, movement and recession of glaciers or ice sheets. A collective term for the geologic processes of glacial activity, including erosion and deposition, and the resulting effects of such action on the earth's surface. GG glacier – (a) A large mass of ice formed, at least in part, on land by the compaction and recrystallization of snow, moving slowly by creep downslope or outward in all directions due to the stress of its own weight, and surviving from year to year. Included are small mountain glaciers as well as ice sheets continental in size, and ice shelves which float on the ocean but are fed in part by ice formed on land. (b) A stream-like landform having the appearance of, or moving like a glacier; e.g., a rock glacier. Compare – snowfield, rock glacier. GG glacier outburst flood – A sudden, often annual, release of meltwater from a glacier or glacier-damned lake sometimes resulting in a catastrophic flood, formed by melting of a drainage channel or buoyant lifting of ice by water or by subglacial volcanic activity; also called jokuhlaup. Compare – scabland, giant ripple. GG glaciofluvial deposit – Material moved by glaciers and subsequently sorted and deposited by streams flowing from the melting ice. The deposits are stratified and may occur in the form of outwash plains, valley trains, deltas, kames, eskers, and kame terraces. Compare – drift and outwash. HP glaciokarst – Karst in glaciated terrain developed on bedrock susceptible to dissolution (e.g., limestone), thinly mantled (e.g., < 5 - 30 m) with drift and characterized by surficial, closed depressions formed by post-glacial, subsurface karstic collapse (e.g., sinkholes) rather than by glacial processes (e.g., ice-block melt-out); common in IN, MI. Compare – karst. SW & GG glaciolacustrine deposit – Material ranging from fine clay to sand derived from glaciers and deposited in glacial lakes by water originating mainly from the melting of glacial ice. Many are bedded or laminated with varves or rhythmites. HP glaciomarine deposit – Glacially eroded, terrestrially derived sediments (clay, silt, sand, and gravel) that accumulated on the ocean floor. Sediments may be accumulated as an ice-contact deposit, by fluvial transport, ice-rafting, or eolian transport. GG & GM glade – (colloquial: Ozark uplands, USA) (a) A largely treeless, open, grassy area (e.g., oak savanna) on high, broad interfluves and hillsides, commonly with shallow soils. Compare – park. SW. (b) (not preferred) refer to park: An ecological term for a grassy, open depression or small valley as in a high meadow; sometimes marshy and forming the headwaters of a stream, or a low, grassy marsh that is periodically inundated. GG & SW glauconite pellets – Silt to sand-sized, nodular aggregates with a characteristic greenish color, dominantly composed of the clay mineral glauconite; formed in near-shore marine sediments and subsequently exposed by a drop in sea level or rise of a land mass, as on a coastal plain. Glauconite pellets have a high potassium content and higher CEC and moisture retention compared to other mineral sands. Compare – greensands. SW gorge – (a) A narrow, deep valley with nearly vertical, rocky walls, smaller than a canyon, and more steep-sided than a ravine; especially a restricted, steep-walled part of a canyon. (b) A narrow defile or passage between hills or mountains. GG graben – An elongate trough or basin bounded on both sides by high-angle, normal faults that dip towards the interior of the trough. It is a structural form that may or may not be geomorphically expressed as a rift valley. Compare – horst, half graben. GG granitoid –(a) In the IUGS classification (International Union of Geological Sciences), a preliminary term (for field use) for a plutonic rock with Q (quartz) between 20 and 60 (%). (b) A general term for all phaneritic igneous rocks (mineral crystals visible unaided and all about the same size) dominated by quartz and feldspars. SW & GG Grady pond – see Carolina Bay. grassy organic materials – see organic materials. gravel pit – A depression, ditch or pit excavated to furnish gravel for roads or other construction purposes; a type of borrow pit. SW greensands – (a) An unconsolidated, near-shore marine sediment containing substantial amounts of dark greenish glauconite pellets, often mingled with clay or sand (quartz may form the dominant constituent); prominent in Cretaceous and Tertiary coastal plain strata of New Jersey, Delaware and Maryland; has been commercially mined for potassium fertilizer. The term is loosely applied to any glauconitic sediment. (b) (not preferred – use glauconitic sandstone) A sandstone consisting of greensand that is commonly poorly cemented, and has a greenish color when unweathered but an orange or yellow color when weathered. Compare – glauconite pellets. SW grike – (not preferred) refer to cutter. groove – A small, natural, narrow drainageway on high angle slopes which separate tertiary spur ridges or mini- interfluves and is a constituent part of rib and groove topography; common in well dissected uplands. Compare – rib. SW ground moraine – (a) Commonly an extensive, low relief area of till, having an uneven or undulating surface, and commonly bounded on the distal end by a recessional or end moraine. (b) A layer of poorly sorted rock and mineral debris (till) dragged along, in, on, or beneath a glacier and deposited by processes including basal lodgment and release from downwasting stagnant ice by ablation. Compare – end moraine, recessional, moraine, terminal moraine. SW ground soil – Any soil at the present-day land surface and actively undergoing pedogenesis, regardless of its history (i.e., relict, exhumed). Compare – buried soil. SW & RR grus – The fragmental products of in situ granular disintegration of granite and granitic rocks, dominated by inter-crystal disintegration. Compare – saprolite. SW & GG accelerated erosion; common in steep terrain, both archaic (e.g., Peru) and modern (e.g., Nepal). Compare – conservation terrace. SW & GSST hill top – (not recommended) use summit. hogback – A sharp-crested, symmetric ridge formed by highly tilted resistant rock layers; a type of homocline produced by differential erosion of interlayered resistant and weak rocks with dips greater than about 25° (or approximately > 45 % slopes). Compare – homoclinal ridge, cuesta. SW & HP Holocene – The epoch of the Quaternary Period of geologic time following the Pleistocene Epoch (from the present to about 10 to 12 thousand years ago); also corresponding (time-stratigraphic) “series” of earth materials. SW homoclinal – [structural geomorphology] (adjective) Pertaining to strata that dip in one direction with a uniform angle. Compare – cuesta, hogback, homoclinal ridge. HP homoclinal ridge – A homocline that forms an asymmetric ridge with a dip slope commonly between 10 to 25º (15 to 45 %). A homoclinal ridge has steeper dip than a cuesta, but lower dip than a hogback. Compare – cuesta, hogback. SW & RF homocline – A general term for a series of rock strata that dip in one direction with a uniform angle; e.g., one limb of a fold, a tilted fault block, or an isocline. Compare – cuesta, homoclinal ridge, hogback. GG hoodoo – A bizarrely shaped column, pinnacle, or pillar of rock produced by differential weathering or erosion in a region of sporadically heavy rainfall. Formation is facilitated by joints and layers of varying hardness. Compare – earth pillar. GG horn – [glacial geology] A high, rocky, sharp pointed, steep-sided, mountain peak with prominent faces and ridges, bounded by the intersecting walls of three or more cirques that have been cut back into the mountain by headward erosion of glaciers. GG horst – An elongate block that is bounded on both sides by normal faults that dip away from the interior of the horst. It is a structural form and may or may not be expressed geomorphically. GG hot spring – A natural, geothermally heated spring whose temperature is above that of the human body. Compare – geyser, mud pot. GG human artifact – (not preferred) see artifact. human-transported material – Organic or mineral soil material (or any other material that can function as a soil material) that has been moved horizontally onto a pedon from a source area outside of that pedon by directed human activity, usually with the aid of machinery. There has been little or no subsequent reworking by wind, gravity, water, or ice. Human-transported materials are most commonly associated with building sites, mining or dredging operations, sanitary landfills, or other similar activities that result in the formation of a constructional anthropogenic landform. ICOMANTH hummock – [geomorphology] (a) (not preferred – see hillock). An imprecise, general term for a rounded or conical mound or other small elevation. (b) (not preferred) A slight rise of ground above a level surface. GG hummock – [patterned ground] A small, irregular knob of earth (earth hummock) or turf (turf hummock). Neither type of hummock is diagnostic of permafrost, but both are most common in subpolar or alpine regions. Both require vegetative cover. GG ice age – (not recommended) use Pleistocene. ice pressure ridge – A rugged, irregular wall of broken floating ice buckled upward by the lateral pressure of wind or current forcing or squeezing one floe against another, or against a shore; it may extend for kilometers in length and up to 30 m in height. Along shores they are lower (< 10 m tall) and contribute to the temporary or permanent formation of a beach berm or a rim of boulders and stones. SW & GG ice-contact slope – A steep escarpment of predominantly glaciofluvial sediment that was deposited against a wall of glacier ice, marking the position of a relatively static ice-margin; an irregular scarp against which glacier ice once rested. Compare – head-of-outwash. SW & GG ice-margin complex – An assemblage of landforms constructed proximal to a relatively static, rapidly wasting continental glacial margin. Constituent landforms can include fosse, head-of-outwash, ice-contact slope, ice- contact delta, kame, kame moraine, kettle, outwash fan, small outwash plain, glacial sluiceway, and small proglacial lake. Moraines, if present, are of limited occurrence (except kame moraines which can be extensive). Glaciofluvial sediments dominate but glaciolacustrine sediments, till, and diamictons can be present in minor amounts. SW ice-marginal stream – A stream drainage along the side or front of a glacier. Relict ice-marginal streams are used to trace the former position of a glacier; also called ice-marginal drainage. SW & GG ice-pushed ridge – An asymmetrical ridge of local, essentially non-glacial material (such as deformed bedrock, with some drift incorporated in it) that has been pressed up by the shearing action of an advancing glacier. It is typically 10 - 60 m high, about 150 - 300 m wide, and as much as 5 km long. Examples are common on the Great Plains where such ridges occur on the sides of escarpments formed of relatively incompetent rocks that face the direction from which the ice moved. GG ice-rafting – The transportation of rock fragments of all sizes on or within icebergs, ice floes, or other forms of floating ice. Compare – dropstone, erratic. GG ice segregation – The formation of ice by the migration of pore water to the frozen fringe where it forms into discrete layers or lenses. It commonly ranges in thickness from hairline to more than 10 m and often occurs in alternating layers of ice and soil. NRC ice wedge – A massive, generally wedge-shaped body with its apex pointing downward, composed of foliated or vertically banded, commonly white, ice. NRC ice wedge cast – A filling of sediment in the space formerly occupied by an ice wedge. NRC ice wedge polygon – Patterned ground in areas of ice wedges. These polygons are commonly in poorly drained areas and may be high-centered or low-centered. NRC igneous rock – Rock formed by cooling and solidification from magma, and that has not been changed appreciably by weathering since its formation; major varieties include plutonic (i.e., intrusive) and volcanic (i.e., extrusive) rocks. Examples: andesite, basalt, granite. Compare – intrusive, extrusive, metamorphic rock. GSST & HP inlet – A short, narrow waterway connecting a bay, lagoon, or similar body of water. Compare – tidal inlet. GG impact crater – (a) [anthropogenic] A generally circular or elliptical depression formed by hypervelocity impact of an experimental projectile or ordinance into earthy or rock material. Compare – caldera, crater, meteorite crater. SW. (b) (not recommended: use meteorite crater) A generally circular crater formed by the impact of an interplanetary body (projectile) on a planetary surface. GG inselberg – A prominent, isolated, residual knob, hill, or small mountain, usually smoothed and rounded, rising abruptly from an extensive lowland erosion surface in a hot dry region; generally bare and rocky although the lower slopes are commonly buried by colluvium. Compare – monadnock, nunatak. GG inset fan – (colloquial: southwestern USA) The flood plain of an ephemeral stream that is confined between the fan remnants, ballenas, basin-floor remnants, or closely-opposed fan toeslopes of a basin. FF & SW integrated drainage – A general term for a drainage pattern in which stream systems have developed to the point where all parts of the landscape drain into some part of a stream system, the initial or original surfaces have essentially disappeared and the region drains to a common base level. Few or no closed drainage systems are present. SW interbedded – Said of beds lying between or alternating with others of different character; especially said of rock material or sediments laid down in sequence between other beds, such as "interbedded" sands and gravels. GG interdrumlin – The concave to relatively flat bottomed, roughly linear depressions ranging from small saddles or swales to small valleys that separate drumlins or drumlinoid ridges in drumlin fields. Streams, if present, have not had a dominant impact on the formation of the depression. Compare – drumlin, drumlinoid ridge. SW interdrumlin swale – see interdrumlin interdune – The relatively flat surface, whether sand-free or sand-covered, between dunes. GG interdune valley – A broad interdune area consisting of a low-lying, relatively flat surface commonly found between very large dunes, and which lies in close proximity to the local groundwater table (if present). SW interfluve – A landform composed of the relatively undissected upland or ridge between two adjacent valleys containing streams flowing in the same general direction. An elevated area between two drainageways that sheds water to those drainageways. Compare – divide. GG & FFP interfluve – [geomorphology] A geomorphic component of hills consisting of the uppermost, comparatively level or gently sloped area of a hill; shoulders of backwearing hillslopes can narrow the upland (e.g., ridge) or merge (e.g., crest, saddle) resulting in a strongly convex shape. Compare – crest, side slope, head slope, nose slope, free face, base slope. SW interfurrow – A low, commonly linear or arcuate ridge of soil mounded between furrows by a plow or other farm equipment and serves as a slightly elevated bedding area for planted crops; also called row, tillage row, tillage ridge, tillage mound. Interfurrows range from narrow and peaked (tillage ridge) to broad and flat-topped; size and shape depends upon how the elevated areas are made and the crop grown. Compare – furrow. SW interior valley – A large, flat-floored closed depression in a karst area whose drainage is ultimately subsurface and its floor is commonly covered by alluvium. Some interior valleys may become ephemeral lakes during periods of heavy rainfall, when sinking streams that drain them cannot manage the runoff; also called polje (not preferred). Compare – karst valley, sinkhole. GG intermediate position – (gilgai) The subsurface location and morphology of the nearly level, transitional area (microslope) between an upwelling morphology (chimney) under a slightly elevated microhigh (i.e., microknoll; mound in Russia) and the bowl morphology under an adjacent microlow (i.e., microbasin, microtrough; kluftkarren – (not preferred) refer to solution fissure. knickpoint – (a) A point of abrupt inflection in the longitudinal profile of a stream or of its valley (e.g., a waterfall); it marks the maximum headward erosion of a new erosion cycle that grades to a new, lower base level. (b) Any interruption or break in slope. SW knob – (a) A rounded eminence, a small hill or mountain; especially a prominent or isolated hill with steep sides, commonly found in the Southern United States. (b) A peak or other projection from the top of a hill or mountain. Also, a boulder or group of boulders or an area of resistant rocks protruding from the side of a hill or mountain. Compare – stack [geom.]. GG knoll – A small, low, rounded hill rising above adjacent landforms. HP lacustrine deposit – Clastic sediments and chemical precipitates deposited in lakes. HP lagoon – A shallow stretch of salt or brackish water, partly or completely separated from a sea or lake by an offshore reef, barrier island, sandbank or spit. GG87. lagoon [relict] – A nearly level, filled trough or depression behind the longshore bar on a barrier beach and built by a receding pluvial or glacial lake. Compare – sewage lagoon, pluvial lake. SW & FFP lagoon bottom – The nearly level or slightly undulating central portion of a submerged, low-energy, depositional estuarine basin (McGinn, 1982) characterized by relatively deep water (1.0 to >2.5 m). Compare – bay bottom. SSS lagoon channel – A subaqueous, sinuous area within a lagoon that likely represents a relict channel (paleochannel) (Wells et al., 1994) that is maintained by strong currents during tidal cycles. SSS lagoonal deposit – Sand, silt or clay-sized sediments transported and deposited by wind, currents, and storm washover in the relatively low-energy, brackish to saline, shallow waters of a lagoon. Compare – estuarine deposit, fluviomarine deposit, marine deposit. SSS lahar – The landform and sediments (i.e., lahar deposit) emplaced by, and the process associated with, a mudflow composed mainly of volcaniclastic debris on or near the flank of a volcano. Sediment composition includes pyroclastic material, primary lava-flow blocks and fragments, and nonvolcanic material. Thick lahar deposits may have crude (poorly sorted) upward-fining strata. A lahar is initially unconsolidated material, but through cementation and compression can become bedrock. Compare – mudflow, andesitic lahar deposit, lahar deposit. SW & GG lahar deposit – Unconsolidated volcaniclastic material emplaced as mudflows on or near the flanks of a volcano. SW lake – [water] An inland body of permanently standing water fresh or saline, occupying a depression on the Earth’s surface, generally of appreciable size (larger than a pond) and too deep to permit vegetation (excluding subaqueous vegetation) to take root completely across the expanse of water. GG lake plain – A nearly level surface marking the floor of an extinct lake filled by well-sorted, generally fine- textured, stratified deposits, commonly containing varves. GG lake terrace – A narrow shelf, partly cut and partly built, produced along a lake shore in front of a scarp line of low cliffs and later exposed when the water level falls. GG lakebed – The bottom of a lake; a lake basin. GG lakebed [relict] – The flat to gently undulating, exposed ground underlain or composed of fine-grained sediments deposited in a former lake. GG lakeshore – The narrow strip of land in contact with or bordering a lake; especially the beach of a lake. GG lamella – (a) [soil] A thin (< 7.5 cm thick), discontinuous or continuous, generally horizontal layer of fine material (especially clay and iron oxides) that has been pedogenically concentrated (illuviated) within a coarser (e.g., sandy), eluviated layer (several centimeters to several decimeters thick). Compare – lamina. SW & ST. (b) [mineralogy] A thin scale, leaf, lamina, or layer, e.g., one of the units of a polysynthetically twinned mineral, such as plagioclase. GG lamina – (noun) The thinnest recognizable layer (commonly < 1 cm thick) of original deposition in a sediment or sedimentary rock, differing from other layers in color, composition, or particle size. Plural=laminae; Several laminae constitute a bed. Compare – lamella. GG lamination – (not recommended) see lamina. landfill – (see sanitary landfill). Compare – dump. landform – Any physical, recognizable form or feature on the earth's surface, having a characteristic shape, internal composition, and produced by natural causes; a distinct individual produced by a set of processes. Landforms can span a large size (e.g., dune encompasses a number of feature including parabolic dune, which is tens-of-meters across and seif dune, which can be up to a 100 kilometers across. Landforms provide an empirical description of the earth's surface features. SW & GG landscape – [soils] A broad or unique land area comprised of an assemblage or collection of landforms that define a general geomorphic form or setting (e.g., mountain range, lake plain, lava plateau, or loess hill) Landforms within a landscape are spatially associated, but may vary in formation processes and age. SW & GSST landslide – A general, encompassing term for most types of mass movement landforms and processes involving the downslope transport and outward deposition of soil and rock materials, caused by gravitational forces and which may or may not involve saturated materials. Names of landslide types generally reflect the dominant process and/or the resultant landform. The main operational categories of mass movement are fall (rockfall, debris fall, soil fall), topple (rock topple, debris topple, soil topple), slide (rotational landslide, block glide, debris slide, lateral spread), flow [rockfall avalanche, debris avalanche, debris flow (e.g., lahar), earthflow, (creep, mudflow)], and complex landslides. Compare – solifluction. SW & DV land-surface form – The description of a given terrain unit based on empirical analysis of the land surface rather than interpretation of genetic factors. Surface form may be expressed quantitatively in terms of vertical and planimetric slope-class distribution, local and absolute relief, and patterns of terrain features such as interfluve crests, drainage lines, or escarpments. HP lapilli – Nonvesicular or slightly vesicular pyroclastics, 2.0 to 76 mm in at least one dimension, with an apparent specific gravity of 2.0 or more g/cm3. Compare – ash, volcanic block, cinders, tephra. KST lateral moraine – A ridge-like moraine carried on and deposited at the side margin of a valley glacier. It is composed chiefly of rock fragments derived from valley walls by glacial abrasion and plucking, or colluvial accumulation from adjacent slopes. GG lateral spread – A category of mass movement processes, associated sediments (lateral spread deposit), or resultant landform characterized by a very rapid spread dominated by lateral movement in a soil or fractured rock mass resulting from liquefaction or plastic flow of underlying materials; also called spread. Types of lateral spreads can be specified based on the dominant particle size of sediments (i.e., debris spread, earth spread, rock spread. Compare – fall, topple, slide, flow, complex landslide, landslide. SW, DV, & GG lava – A general term for a molten extrusive, also the rock solidified from it. Compare – aa lava, block lava, pahoehoe lava, pillow lava. GG lava channel – see lava trench. lava dome – A rounded or irregular mound, hill or small mountain composed of lava congealed over a volcanic vent on the flanks or within a crater or caldera. Typically composed of silica-rich volcanic rocks (e.g., rhyolite, dacite) with admixtures of obsidian, agglomerate, volcanic breccia, etc. The lava may be uniform or varied in color and texture; also called a resurgent dome. SW, HS, & GG lava field – An area covered primarily by lava flows whose terrain can be rough and broken or relatively smooth; it can include vent structures (e.g., small cinder cones, spatter cones, etc.), surface flow structures (e.g., pressure ridges, tumuli, etc.) and small, intermittent areas covered with pyroclastics. Compare – lava plain, volcanic field. SW lava flow – A solidified body of rock formed from the lateral, surficial outpouring of molten lava from a vent or fissure, often lobate in form. Compare – aa lava flow, lava flow unit, pahoehoe lava flow. GG lava flow unit – A separate, distinct lobe of lava that issues from the main body of a lava flow; a specific outpouring of lava, a few centimeters to several meters thick and of variable lateral extent that forms a subdivision within a single flow. A series of overlapping lava flow-units together comprise a single lava flow. Also called flow unit. Compare – lava flow. GS & GG lava plain – A broad area of nearly level land, that can be localized but is commonly hundreds of square kilometers in extent, covered by a relatively thin succession of primarily basaltic lava flows resulting from fissure eruptions. Compare – lava plateau, lava field, volcanic field. SW & GG lava plateau – A broad elevated tableland or flat-topped highland that may be localized but commonly is many hundreds or thousands of square kilometers in extent, underlain by a thick succession of basaltic lava flows resulting from fissure eruptions (e.g., Columbia River Plateau). Compare – lava plain, lava field. GG lava trench – A natural surface channel in a lava flow that never had a roof, formed by the surficial draining of molten lava rather than by erosion from running water; also called lava channel. Compare – mawae, lava tube. SW lava tube – A natural, hollow tunnel beneath the surface of a solidified lava flow through which the lava flow was fed; the tunnel was left empty when the molten lava drained out. MA & GG ledge – (a) A narrow shelf or projection of rock, much longer than wide, formed on a rock wall or cliff face, as along a coast by differential wave action on softer rocks; erosion is by combined biological and chemical weathering. (b) A rocky outcrop; solid rock. (c) A shelf-like quarry exposure or natural rock outcrop. Compare – structural bench. GG lee – (adjective) Said of a side or slope that faces away from an advancing glacier or ice sheet, and facing the downstream (“down-ice”) side of a glacier and relatively protected from its abrasive action. Compare – stoss, stoss and lee, crag and tail. GG mainland cove – A subaqueous area adjacent to the mainland or a submerged mainland beach that forms a minor recess or embayment within the larger basin. Compare – cove, barrier cove. SSS mangrove swamp – A tropical or subtropical marine swamp formed in a silty, organic, or occasionally a coralline substratum and characterized by abundant mangrove trees along the seashore in a low area of salty or brackish water affected by daily tidal fluctuation but protected from violent wave action by reefs or land; dominated by saturated soils, commonly Fluvaquents formed in marl. SW & GG marine deposit – Sediments (predominantly sands, silts and clays) of marine origin; laid down in the waters of an ocean. Compare – estuarine deposit, lagoonal deposit. SW marine lake – [water] An inland body of permanently standing brackish or saline water, occupying a depression on the Earth’s surface whose water level is commonly influenced by ocean tides through subterranean cavities connecting to nearby lagoons; generally of appreciable size (larger than a pond) and too deep to permit emergent vegetation to take root completely across the expanse of water. Such water bodies can have unique biota (e.g., sting-less jellyfish of Palau). SW marine terrace – A constructional coastal strip, sloping gently seaward, veneered by marine deposits (typically silt, sand, fine gravel). Compare – terrace, wave-built terrace. GG marl – A generic term loosely applied to a variety of materials, most of which occur as an earthy, unconsolidated deposit consisting chiefly of an intimate mixture of clay and calcium carbonate formed commonly by the chemical action of algae mats and organic detritus (periphyton); specifically an earthy substance containing 35 to 65 % clay and 65 to 35 % calcium carbonate mud; formed primarily under freshwater lacustrine conditions, but varieties associated with more saline environments and higher carbonate contents also occur. Compare – coastal marl, freshwater marl. SW & HP marsh – Periodically wet or continually flooded areas with the surface not deeply submerged. Covered dominantly with sedges, cattails, rushes, or other hydrophytic plants. Compare – salt marsh, swamp, bog, fen. GSST mass movement – A generic term for any process or sediments (mass movement deposit) resulting from the dislodgment and downslope transport of soil and rock material as a unit under direct gravitational stress. The process includes slow displacements such as creep and solifluction, and rapid movements such as landslides, rock slides, and falls, earthflows, debris flows, and avalanches. Agents of fluid transport (water, ice, air) may play an important, if subordinate role in the process. HP mass-movement till – (not preferred) refer to till. mass wasting – (not preferred) refer to mass movement. mawae – (colloquial: Hawaii) A natural surface channel commonly found near the middle of an a'a lava flow, formed by the surficial draining of molten lava rather than by erosion from running water; a type of lava trench. Compare – lava tube. MA meander – [streams] One of a series of regular freely developing sinuous curves, bends, loops, turns, or windings in the course of a stream. GG meander belt – The zone within which migration of a meandering channel occurs; the flood plain area included between two imaginary lines drawn tangential to the outer bends of active channel loops. Landform components of the meander-belt surface are produced by a combination of gradual (lateral and down-valley) migration of meander loops and avulsive channel shifts causing abrupt cut-offs of loop segments. Landforms flanking the sinuous stream channel include: point bars, abandoned meanders, meander scrolls, oxbow lakes, natural levees, and flood-plain splays. Meander belts may not exhibit prominent natural levee or splay forms. Flood plains of broad valleys may contain one or more abandoned meander belts in addition to the zone flanking the active stream channel. HP meander scar – (a) A crescent-shaped, concave or linear mark on the face of a bluff or valley wall, produced by the lateral erosion of a meandering stream which impinged upon and undercut the bluff; if it’s no longer adjacent to the modern stream channel it indicates an abandoned route of the stream. SW. (b) (not recommended: refer to oxbow) An abandoned meander, commonly filled in by deposition and vegetation, but still discernable. GG meander scroll – (a) One of a series of long, parallel, close fitting, crescent-shaped ridges and troughs formed along the inner bank of a stream meander as the channel migrated laterally down-valley and toward the outer bank. Compare – meander belt, point bar. (b) (not recommended: use oxbow lake) A small, elongate lake on a flood plain in a well-defined part of an abandoned stream channel. GG meandering channel – The term "meandering" should be restricted to loops with channel length more than 1.5 to 2 times the meander wave length. Meandering stream channels commonly have cross sections with low width- to-depth ratios, cohesive (fine-grained) bank materials, and low gradient. At a given bank-full discharge, meandering streams have gentler slopes, and deeper narrower, and more stable channel cross sections than braided streams. Compare – meander, braided stream, flood-plain landforms. HP & RR medial moraine – (a) An elongate moraine carried in or upon the middle of a glacier and parallel to its sides, usually formed by the merging of adjacent and inner lateral moraines below the junction of two coalescing valley glaciers. (b) A moraine formed by glacial abrasion of a rocky protuberance near the middle of a glacier and whose debris appears at the glacier surface in the ablation area. (c) The irregular ridge left behind in the middle of a glacial valley, when the glacier on which it was formed has disappeared. GG melt-out till – A till that may be either subglacial or supraglacial in origin. Melt-out till forms by slow melting of debris-rich stagnant ice, but without secondary flow processes. The fabric and clast orientations, imparted by ice processes, remain mostly intact. Compare – subglacial till, supraglacial till, flow till, lodgment till. GG mesa –An isolated, flat-topped landform that stands distinctly above the adjacent land area and is bounded by steep slopes or cliffs; and is generally capped by erosion-resistant, nearly horizontal rock (often lava). Mesas and buttes have similar forms and isolated occurrence. A mesa has a summit area broader than the bounding cliff height. Mesas are most common in arid and semiarid regions, but are not climatically restricted. Compare – butte, plateau, cuesta. HP & GG metamorphic rock – Rock of any origin altered in mineralogical composition, chemical composition, or structure by heat, pressure, and movement at depth in the earth's crust. Nearly all such rocks are crystalline. Examples: schist, gneiss, quartzite, slate, marble. HP metasediment – A sediment or sedimentary rock that shows evidence of having been subjected to metamorphism. GG meta-stable slope – (not recommended: obsolete) A slope that is relatively stable at the present time, but may become active if the environmental balance is disturbed, for instance, by road construction or destruction of vegetation. A metastable slope is often related to base levels of former geomorphic episodes. The regolith is generally moderately deep, may contain stone lines or relict evidence of slope alluvium. Slope gradients usually range from 15 to 45 %. Compare – active slope. HP meteorite crater – An impact crater formed by the falling of a large meteorite onto the earth’s surface; e.g., Barringer Crater (AZ). Compare – crater, impact crater. SW & GG microbiotic crust – A thin, surface layer (crust) of soil particles bound together primarily by living organisms and their organic byproducts; thickness can range up from < 1 cm up to 10 cm; aerial coverage of the ground surface can range from 10 to 100 %. Crusts stabilize loose earthy material. Other types of surface crusts include chemical crusts (e.g., salt crusts) and physical crusts (e.g., raindrop-impact crust). SW & SS micro-depression – (not preferred) refer to microlow. microfeature – [soil survey] Small, local, natural forms (features) on the land surface that are too small to delineate on a topographic or soils map at commonly used map scales (e.g., 1:24,000 to 1:10,000). Examples include earth pillar, patterned ground, frost boil. Compare – microrelief. SW microhigh – A generic microrelief term applied to slightly elevated areas relative to the adjacent ground surface; differences in relief range from several centimeters to several meters. Cross-sectional profiles can be simple or complex and generally consist of gently rounded, convex tops with gently sloping sides; also spelled micro-high. SW micro-knoll – (not preferred) refer to microhigh. microlow – A generic microrelief term applied to slightly lower areas relative to the adjacent ground surface (e.g., shallow depression); differences in relief range from several centimeters to several meters. Cross-sectional profiles can be simple or complex and generally consist of subdued, concave, open or closed depressions with gently sloping sides; also spelled micro-low. SW microrelief – (a) [soil survey] Slight variations in the height of a land surface that are too small or intricate to delineate on a topographic or soils map at commonly used map scales (e.g., 1:24,000 through 1:10,000). Examples include microhigh, microslope, and microlow. Compare – microfeature. SW. (b) (not preferred - refer to microfeature) Generically refers to local, slight irregularities in form and height of a land surface that are superimposed upon a larger landform, including such features as low mounds, swales, and shallow pits. GG microslope – A generic microrelief term applied to areas of nominal surface relief (slightly sloping to level), relative to the adjacent ground surface; differences in overall local relief range from several centimeters to several meters. Cross-sectional profiles can be simple or complex and generally consist of low and gently rounded, convex tops (microhigh), gently sloping to level sides (microslope), and depressional low areas (microlow). Microslopes commonly constitute the majority of the land surface area in gilgai and other settings with microrelief. SW midden – A mound or stratum of refuse (broken pots, ashes, food remains, etc.) normally found on the site of an ancient settlement. GG mima mound – A term used for one of numerous low circular or oval domes composed of loose, unstratified, gravelly, silty, or sandy material. The basal diameter varies from 3 meters to more than 30 meters, and the height from 30 centimeters to about 2 meters. Compare – pimple mound, patterned ground, shrub-coppice dune. GG mine spoil, coal extraction – Randomly mixed, earthy materials artificially deposited as a result of either surficial or underground coal mining activities; a type of mine spoil. SW mine spoil, metal-ore extraction – Randomly mixed, earthy materials artificially deposited as a result of either surficial or underground metal-ore mining activities; a type of mine spoil. SW mine spoil or earthy fill – [soil survey] An accumulation of displaced earthy material, rock, or other waste material removed during mining or excavation. SW & GSST mud flat – (not preferred – use tidal flat) A relatively level area of fine grained material (e.g., silt) along a shore (as in a sheltered estuary) or around an island, alternately covered and uncovered by the tide or covered by shallow water, and barren of vegetation. Compare – low marsh, tidal flat, tidal marsh. GG mud pot – A type of hot spring containing boiling mud, usually sulfurous and often multicolored, as in a paint pot. Mud pots are commonly associated with geysers and other hot springs in volcanic areas, especially in Yellowstone Natl. Park, WY. Compare – geyser, hot spring. GG mudflow – The mass movement process, associated sediments (mudflow deposit), or resultant landform characterized by a very rapid type of earthflow dominated by a sudden, downslope movement of a saturated mass of rock, soil, and mud (more than 50 % of the particles are < 2 mm), that behaves as much as a viscous fluid when moving. Compare – debris flow, flow, landslide. SW & DV mudstone – (a) A blocky or massive, fine-grained sedimentary rock in which the proportions of clay and silt are approximately equal. (b) A general term that includes clay, silt, claystone, siltstone, shale, and argillite, and that should be used only when the amounts of clay and silt are not known or cannot be precisely identified. GG muskeg – A bog, usually a sphagnum bog, frequently with grassy tussocks (hummocks), growing in wet, poorly drained boreal regions, with deep accumulations of organic material, often in areas of permafrost; a moss-covered muck or peat bog of boreal regions. GG and HP natural levee – A long, broad low ridge or embankment of sand and coarse silt, built by a stream on its flood plain and along both sides of its channel, especially in time of flood when water overflowing the normal banks is forced to deposit the coarsest part of its load. It has a gentle slope away from the river and toward the surrounding floodplain, and its highest elevation is closest to the river bank. Compare – levee, artificial levee, meander belt. GG nearshore zone – A subaqueous marine or lacustrine landform area that generally parallels the shore and extends seaward or lakeward from the low water line to beyond the breaker zone including longshore bars. In the nearshore zone, waves steepen, break, and reform during passage to the beach. Sediment transport occurs both along and perpendicular to the shore via wave and current action. Compare – nearshore zone [relict]. SW & RF nearshore zone [relict] – A former nearshore zone now subaerially exposed due to isostatic rebound or glacial lake drainage. Commonly a raised beach marks the former landward edge of a relict nearshore zone and relict longshore bars may exist in offshore positions. Surficial sediments may display evidence of wave and current action such as sorting or particle-size discontinuities. SW neck [volcanic] – (not preferred) refer to volcanic neck. net (nonsorted) – (not preferred) refer to patterned ground. net (sorted) – (not preferred) refer to patterned ground. nivation – The process of excavation of a shallow depression or nivation hollow on a mountain side by removal of fine material around the edge of a shrinking snow patch or snow bank, chiefly through sheetwash, rivulet flow, and solution in melt water. Freeze-thaw action is apparently insignificant. GG nivation hollow – A shallow, non-cliffed depression or hollow on a mountain side permanently or intermittently occupied by a snow bank or snow patch and produced by nivation. If the snow completely melts each summer the hollow is deepened; otherwise not; may be a cirque precursor if further enlarged and deepened by alpine glaciation. GG nonsorted circle – A type of patterned ground whose mesh (shape) is dominantly circular and has a nonsorted appearance due to the absence of a border of rock fragments. Vegetation characteristically outlines the pattern by forming a bordering ridge. Diameters commonly range from 0.5 to 3 m. Nonsorted circles include mud boils, earth hummocks, turf hummocks, and frost boils. Nonsorted circles have various origins. Some, such as mud and earth hummocks and frost boils, involve cryoturbation activity and differential heave of frost-susceptible materials. Others, such as mud boils, involve hydraulic pressures and diapir-like displacement of water-saturated sediments. Compare – sorted circle, frost boil, patterned ground. NRC & GG nonsorted polygon – (not preferred) refer to patterned ground. nose slope – [geomorphology] A geomorphic component of hills consisting of the projecting end (laterally convex area) of a hillside, resulting in predominantly divergent overland water flow (e.g., sheet wash); contour lines generally form convex curves. Nose slopes are dominated by colluvium and slope wash sediments (e.g., slope alluvium). Slope complexity (downslope shape) can range from simple to complex. Nose slopes are comparatively drier portions of hillslopes and tend to have thinner colluvial sediments and profiles. Compare – head slope, side slope, free face, interfluve, crest, base slope. SW notch – (a) (colloquial: northeastern USA) A narrow passageway, or short defile between mountains; a deep, close pass. Compare – gap. (b) A breached opening in the rim of a volcanic crater. GG novaculite – A dense, even-textured, extremely finely grained, siliceous, sedimentary rock recrystallized from chert with microcrystalline quartz dominant over chalcedony (cryptocrystalline quartz). It is hard, white to grayish-black in color, translucent on thin edges, has a dull to waxy luster, and displays smooth conchoidal fracture when broken. Novaculite occurs in the Ouachita Mountains of AR and OK and the Marathon Uplift of TX where it forms erosion resistant ridges. At the Ouachita Mountain type occurrence, novaculite formed by low-grade, thermal metamorphism of bedded chert. This rock serves widely as a whetstone or oilstone. Compare – chert. SW & GG nuée ardente – A swiftly flowing, turbulent gaseous cloud, sometimes incandescent, erupted from a volcano and containing ash and other pyroclastics in its lower part; a density current of pyroclastic flow. Compare – pyroclastic flow, lahar. GG nunatak – An isolated hill, knob, ridge, or peak of bedrock that projects prominently above the surface of a glacier and is completely surrounded by glacier ice. Compare – inselberg, monadnock. GG Occam’s razor – The philosophical principle of parsimony: the simplest explanation of natural phenomena (or the use of the minimum number of assumptions) until new information requires otherwise, is most likely the correct one; also spelled Ockham’s. GG ocean – The continuous salt-water body that surrounds the continents and fills the Earth’s great depressions; also, one of its major geographic divisions. Compare – sea. GG offshore bar – (not recommended) use barrier beach. Oligocene – An epoch of the Tertiary Period of geologic time (from 23.3 to 35.4 million years ago), which follows the Eocene Epoch and precede the Miocene Epoch; also the corresponding (time-stratigraphic) “series” of earthy materials. SW open depression – A generic name for any enclosed or low area that has a surface drainage outlet whereby surface water can leave the enclosure; an area of lower ground indicated on a topographic map by contour lines forming an incomplete loop or basin indicating at least one surface exit. Compare – closed basin. SW openpit mine – A relatively large depression resulting from the excavation of material and redistribution of overburden associated with surficial mining operations. Compare – quarry, surface mine. SW & GG organic materials – [soil survey] Unconsolidated sediments or deposits in which carbon is an essential, substantial component. Several types of organic materials (deposits) can be identified based on the composition of the dominant fibers (grassy organic materials, herbaceous organic materials, mossy organic materials, woody organic materials). Compare – herbaceous peat, moss peat, sedimentary peat, woody peat. SW outcrop – (a) That part of a geologic formation or structure that appears at the surface of the earth. (b) [soil survey] An actual exposure of bedrock at or above the ground surface; the miscellaneous area rock outcrop. Compare – cliff, slickrock. SW & GG outwash – [glacial geology] Stratified and sorted sediments (chiefly sand and gravel) removed or "washed out" from a glacier by melt-water streams and deposited in front of or beyond the end moraine or the margin of a glacier. The coarser material is deposited nearer to the ice. Compare – pitted outwash, drift, esker, kame, till. SW & GG outwash delta – A relict (inactive) delta composed of glaciofluvial sediments formed where a sediment laden outwash river emptied into an open lake, commonly a proglacial lake. Sediment attributes include very gently dipping topset beds (coarser textures) and steeply dipping foreset beds (finer textures). SW & GM outwash fan – A fan-shaped accumulation of outwash deposited by meltwater streams in front of the end or recessional moraine of a glacier. Coalescing outwash fans form an outwash plain. GG outwash plain – An extensive lowland area of coarse textured, glaciofluvial material. An outwash plain is commonly smooth; where pitted, due to melt-out of incorporated ice masses (pitted outwash plain), it is generally low in relief and largely retains its original gradient. Compare – outwash, pitted outwash plain, collapsed outwash plain, kettles; also called sandur. SW & HP outwash terrace – A flat-topped bank of outwash with an abrupt outer face (scarp or riser) extending along a valley downstream from an outwash plain or terminal moraine; a valley train deposit. Compare – kame terrace, valley train. SW overbank deposit – Fine-grained sediments (silt and clay) deposited from suspension on a flood plain by floodwaters that cannot be contained within the stream channel. GG overburden – (a) The upper part of a sedimentary deposit, compressing and consolidating the materials below. (b) The loose soil or other unconsolidated material overlying bedrock, either transported or formed in place (synonym for regolith). GG overflow stream channel – A watercourse that is generally dry but conducts flood waters that have overflowed the banks of a river, commonly from large storms, annual meltwater, or glacial meltwaters. SW overprinting – The process of superimposing a new set of features over a preexisting set due to a shift in environmental conditions such as a change in climate or local hydrology. The resulting composite morphology retains features that would not form under present conditions. Compare – overprinted soil. SW overprinted soil – A soil in which new soil morphology has developed and is superimposed upon that of a pre- existing soil due to a shift in pedogenic conditions such as a change in climate or hydrology; the composite morphology retains some relict features that would not form under present day conditions. Sometimes called welded soil (not preferred). SW of material eroded (e.g., bedrock = rock pediment, or regolith = pediment). or (c) combinations of the above. Compare – rock pediment, Piedmont slope, structural bench. SW, HP, & RR pedisediment – A sediment layer, eroded from the shoulder and backslope of an erosional slope that lies on and is, or was, being transported across a pediment. FFP pedoturbation – The mixing of soil materials by natural processes. Compare – cryoturbation. BHM peneplain – (not recommended: obsolete) A low nearly featureless, gently undulating land surface of considerable area, which presumably has been produced by the processes of long-continued subaerial erosion. GG peninsula – (a) An elongated body or stretch of land nearly surrounded by water (e.g., on three sides) and connected with a larger tract of land area, usually by a neck or an isthmus. (b) A relatively large tract of land jutting out into the water, with or without a well-defined isthmus; e.g., the Italian peninsula. GG perennial stream – A stream or reach of a stream that flows continuously throughout the year and whose surface is generally lower than the water table adjacent to the region adjoining the stream. Compare – Ephemeral stream, Intermittent stream. GG periglacial – (adjective) Pertaining to processes, conditions, areas, climates, and topographic features occurring at the immediate margins of glaciers and ice sheets, and influenced by cold temperature of the ice. The term was originally introduced to designate the climate and related geologic features peripheral to ice sheets of the Pleistocene. HP permafrost – Ground, soil, or rock that remains at or below 0 °C for at least two years. It is defined on the basis of temperature and is not necessarily frozen (i.e., cemented by ice). Compare – continuous permafrost, discontinuous permafrost, sporadic permafrost, thaw-sensitive permafrost, thaw-stable permafrost. NRC Physiographic Division – A large portion of a continent of which all parts are similar in geologic structure and climate at a small scale (e.g., 1:5,000,000) and which has consequently had a unified geomorphic history and whose pattern of relief or landforms differ significantly from that of adjacent areas. Examples: the Laurentian Upland, Rocky Mountain System, and Interior Highlands of the USA western USA [The highest level in the Physiographic Location part of the Geomorphic Description System]. SW Physiographic Province – A region of which all parts are similar in geologic structure and climate and which has consequently had a unified geomorphic history; a region whose pattern of relief or landforms differ significantly from that of adjacent regions; i.e., a subset within a Physiographic Division. Examples: the Valley and Ridge, Blue Ridge, and Piedmont provinces in the eastern USA, and the Basin and Range, Rocky Mountains, and Great Plains provinces in the western USA [The second highest level in the Physiographic Location part of the Geomorphic Description System]. SW & GG Physiographic Section – An area which all parts are similar in geologic structure and climate at a relatively small scale and which has consequently had a unified geomorphic history, and whose pattern of relief or landforms differ significantly from that of adjacent areas ( = Fenneman's (1957) "Section"); i.e., a subset within a Physiographic Province). Examples: the Mohawk, Green Mountain, and Floridian Sections in the eastern USA and the Sacramento Section, Puget Trough, and Klamath Mountains in the western USA [The third highest level in the Physiographic Location part of the Geomorphic Description System]. SW piedmont – (adjective) Lying or formed at the base of a mountain or mountain range; e.g., a piedmont terrace or a piedmont pediment. (noun) An area, plain, slope, glacier, or other feature at the base of a mountain; e.g., a foothill or a bajada. In the United States, the Piedmont (noun) is a low plateau extending from New Jersey to Alabama and lying east of the Appalachian Mountains. GG piedmont slope – (colloquial: western USA) The dominant gentle slope at the foot of a mountain; generally used in terms of intermontane-basin terrain in arid to subhumid regions. Main components include: 1) An erosional surface on bedrock adjacent to the receding mountain front (pediment, rock pediment); 2) A constructional surface comprising individual alluvial fans and interfan valleys, also near the mountain front; and 3) A distal complex of coalescent fans (bajada), and alluvial slopes without fan form. Piedmont slopes grade to basin-floor depressions with alluvial and temporary lake plains or to surfaces associated with through drainage (e.g., axial streams). Compare – bolson, fan piedmont. HP pillow lava – A general term for lava displaying pillow structure (discontinuous, close-fitting, bun-shaped or ellipsoidal masses, generally < 1 m in diameter); considered to have formed in a subaqueous environment; such lava is usually basaltic or andesitic. Compare – aa lava, block lava, pahoehoe lava. SW, GG, & GS pillow lava flow – A lava flow or body displaying pillow structure and considered to have formed in a subaqueous environment (underwater); usually basaltic or andesitic in composition. Compare – aa lava flow, block lava flow, pahoehoe lava flow. SW & GS pimple mound – (colloquial: Gulf Coast USA) Low, flattened, approximately circular or elliptical features composed of sandy loam that is coarser than, and distinct from, the surrounding soil; the basal diameter ranges from 3 m to more than 30 m, and the height from 30 cm to more than 2 m. Compare – mima mound, patterned ground, shrub-coppice dune. GG pingo – A large frost mound; especially a relatively large conical mound of soil-covered ice (commonly 30 to 50 meters high and up to 400 meters in diameter) raised in part by hydrostatic pressure within and below the permafrost of Arctic regions, and of more than 1 year's duration. GG pinnacle – [geomorphology] A tall, slender, tapering tower or spire-shaped pillar of rock, either isolated, as on steep slopes or cliffs formed in karst or other massive rocks, or at the summit of a hill or mountain. Compare – erosional remnant, hoodoo. SW, GG, & WW pinnate drainage pattern – A variation of the dendritic drainage pattern in which the main stream receives many closely spaced, subparallel tributaries that join it at slightly acute angles upstream, resembling in plan a feather. They typically form on steep slopes with soils that have a high silt content; such as loess landscapes or fine-textured flood plains. SW, GG, & WA pit and mound topography – (not recommended) use tree-tip pit and mound topography. pitted outwash – Outwash deposits with surficial pits or kettles, produced by the partial or complete burial of glacial ice by outwash and the subsequent thaw of the ice and collapse of the surficial materials. Compare – pitted outwash plain. GG pitted outwash plain – An outwash plain marked by many irregular depressions such as kettles, shallow pits, and potholes which formed by melting of incorporated ice masses; much of the gradient and internal structures of the original plain remain intact; many are found in WI, MN, MI, and IN. Compare – collapsed outwash plain, outwash, pitted outwash. GG pitted outwash terrace – A relict glaciofluvial terrace that retains its original attitude, composed of undistorted outwash sediments and depositional structures and whose surface is pock-marked with numerous potholes or kettle depressions. Compare – collapsed outwash plain. SW plain – A general term referring to any flat, lowland area, large or small, at a low elevation. Specifically, any extensive region of comparatively smooth and level gently undulating land. A plain has few or no prominent hills or valleys but sometimes has considerable slope, and usually occurs at low elevation relative to surrounding areas. Where dissected, remnants of a plain can form the local uplands. A plain may be forested or bare of trees and may be formed by deposition or erosion. Compare – lowland, plateau. SW & GG plateau – [geomorphology] A comparatively flat area of great extent and elevation; specifically an extensive land region considerably elevated (more than 100 meters) above adjacent lower-lying terrain, and is commonly limited on at least one side by an abrupt descent, has a flat or nearly level surface. A comparatively large part of a plateau surface is near summit level. Compare – hill, foothill, mountain, mesa, plain. GG playa – The usually dry and nearly level lake plain that occupies the lowest parts of closed depressions, such as those occurring on intermontane basin floors. Temporary flooding occurs primarily in response to precipitation- runoff events. Playa deposits are fine grained and may or may not have high water table and saline conditions. HP playa dune – (colloquial: Southern High Plains) A linear or curvilinear ridge of windblown, granular material (generally sand or parna) removed from the adjacent basin by wind erosion (deflation), and deposited on the leeward (prevailing downwind) margin of a playa, playa basin, or salina basin. The dune may be barren or vegetated. Compare – dune. SW playa floor – (colloquial: Southern High Plains) The lowest extensive, flat to slightly concave surface within a playa basin, consisting of a dry lake bed or lake plain underlain by stratified clay, silt or sand, and commonly by soluble salts. Compare – playa step. SW playa lake – A shallow, intermittent lake in a arid or semiarid region, covering or occupying a playa in the wet season but drying up in summer; an ephemeral lake that upon evaporation leaves or forms a playa. GG playa rim – (colloquial: Southern High Plains) The convex, upper margin (shoulder) of a playa basin where the playa slope intersects the surrounding terrain. Compare – playa slope. SW playa slope – (colloquial: Southern High Plains) The generally concave to slightly convex area within a playa basin that lies between the relatively level playa floor below (or playa step, if present) and the convex playa rim above. Overland flow is typically parallel down slope. Compare – playa step, playa rim. SW playa step – (colloquial: Southern High Plains) The relatively level or gently inclined “terrace-like” bench or toeslope within a large playa basin flanking and topographically higher than the playa floor and below the playa slope; a bench or step-like surface within a playa basin that breaks the continuity of the playa slope and modified by erosion and/or deposition. Temporary ponding may occur in response to precipitation / runoff events. Compare – playa slope. SW playette – A very small, playa-like, shallow, closed depression typically with a salt-encrusted surface, little or no vegetation in semiarid to arid climates and infrequently subject to ponding from precipitation events; commonly lacks the component parts of a playa except for a small playa floor. Compare – playa. SW & GHG Pleistocene – The epoch of the Quaternary Period of geologic time (from about 10 to 12 thousand to 1.6 million years ago), following the Pliocene Epoch and preceding the Holocene also the corresponding (time-stratigraphic) "series" of earth materials. SW & HP Pliocene – The last epoch (from 1.6 to 5.2 million years ago) of the Tertiary Period of geologic time that follows the Miocene and precedes the Pleistocene Epoch; also, the corresponding (time-stratigraphic) "series" of earth materials. HP Quaternary – The period of the Cenozoic Era of geologic time, extending from the end of the Tertiary Period (about 1.6 million years ago) to the present and comprising two epochs, the Pleistocene (Ice Age) and Holocene (Recent); also, the corresponding (time-stratigraphic) "series" of earth materials. GG radial drainage pattern – A drainage pattern in which consequent streams radiate or diverge outward, like the spokes of a wheel from a high central area.; a major collector stream is usually found in a curvilinear alignment around the bottom of the elevated topographic feature. It is best developed on the slopes of a young domal structure, a volcanic cone, or isolated hills (erosional remnant). SW, GG, & WA railroad bed – The trace or track of a railroad route, commonly constructed slightly above the adjacent land, and composed mostly of earthy materials (gravel, rock fragments, etc.). Abandoned or reclaimed beds may no longer be topographically or visually distinct, but the materials used to construct them may still be a significant portion of the soil zone. SW raised beach – An ancient (relict) beach occurring above the present shoreline and separated from the present beach, having been elevated above the high-water mark either by local crustal movements (uplift) or by lowering of sea or lake level, and which may be bounded by inland cliffs. GG raised bog – An area of acid, peaty soil especially that developed from moss, in which the center is higher than the margins. Compare – pocosin, Carolina Bay, moss peat. [Note: raised peat bog (not preferred) – refer to highmoor bog]. SW & GG87 ravine – A small stream channel; narrow, steep-sided, commonly V-shaped in cross section and larger than a gully, cut in unconsolidated materials. General synonym (not preferred) – gulch. Compare – arroyo, draw, gully. HP recessional moraine – An end or lateral moraine, built during a temporary but significant halt in the final retreat of a glacier. Also, a moraine built during a minor readvance of the ice front during a period of general recession. Compare – end moraine, ground moraine, terminal moraine. GG reclaimed land – (a) A land area composed of earthy fill material that has been placed and shaped to approximate natural contours, commonly part of land-reclamation efforts after mining operations. (b) A land area, commonly submerged in its native state, that has been protected by artificial structures (e.g., dikes) and drained for agricultural or other purposes (e.g., polder). SW rectangular drainage pattern – A drainage pattern in which the tributaries join the main streams at right-angles, and exhibit sections of approximately the same length which form rectangular shapes; it is indicative of streams following prominent bedrock fault, joint, or foliation systems that break the rocks into rectangular blocks. It is more irregular than the trellis drainage pattern, as the side streams are not perfectly parallel and not necessarily as conspicuously elongated, and secondary tributaries need not be present. The stronger or more harsh the pattern, the thinner the soil cover. These patterns commonly form in slate, schist, and gneiss, in resistive sandstone in arid climates, or in sandstone in humid climates if little soil has developed. SW, GG, & WA reef – A ridge-like or mound-like structure, layered or massive, built by sedentary calcareous organisms, especially corals, and consisting mostly of their remains; it is wave-resistant and stands above the surrounding contemporaneously deposited sediment. Reefs can also include a mass or ridge of rocks, especially coral and sometimes sand, gravel, or shells, rising above the surrounding estuary, sea or lake bottom to or nearly to the surface. SSS, SW, & GG regolith – All unconsolidated earth materials above the solid bedrock. It includes material weathered in place from all kinds of bedrock and alluvial, glacial, eolian, lacustrine, and pyroclastic deposits. Soil scientists regard as soil only that part of the regolith that is modified by organisms and soil-forming processes. Most engineers describe the whole regolith, even to a great depth, as "soil." Compare – residuum, bedrock. HP relict – (adjective) Pertaining to surface landscape features e.g., landforms, geomorphic surfaces, and paleosols that have never been buried and yet are predominantly products of past environments. Compare – exhumed, buried, ground soil. HP relict-tidal inlet – (not preferred) see tidal inlet [relict] relief – The relative difference in elevation between the upland summits and the lowlands or valleys of a given region. Compare – local relief. GG remnant – (not preferred) refer to erosion remnant. residuum – (residual soil material) Unconsolidated, weathered, or partly weathered mineral material that accumulates by disintegration of bedrock in place. Compare – colluvium, regolith, saprolite. HP reworked lake plain – (obsolete) – See till-floored lake plain. rhythmite – An individual unit of a succession of beds developed by rhythmic sedimentation; e.g., a cyclothem. The term implies no limit as to bedding thickness or complexity and denotes no time or seasonal connotation. Compare – varves, cyclothem. GG rib – A small, high angle, tertiary spur ridge or mini-interfluve that is a constituent part of rib & groove topography; (slopes generally 20 - 90 %, ); common on the mid and lower hillslopes of well dissected uplands. Compare – finger ridge, groove, rib and groove topography. SW rib and groove topography – A local scale topography composed of repeating, small, high-angle (slopes generally 20 - 90 %), tertiary spur ridges or mini-interfluves (ribs) separated by small, natural, narrow drainageways (grooves); the overall effect is a corrugated transverse surface, common on the mid and lower slopes of well dissected uplands in semiarid to humid environments (e.g., Basin and Range, Ozarks, etc.). Micro- elevational differences generally range from < 3 to < 15 m. SW ribbed fen – A nutrient-rich wetland with a surface pattern of ridges and depressions. rice paddy – An anthropogenic, nearly level impoundment that is inundated for long periods typically for wetland rice production. It is applied to areas that have been used in this fashion for a long enough period of time to significantly change the original soil morphology (especially redoximorphic features). SW ridge – A long, narrow elevation of the land surface, usually sharp crested with steep sides and forming an extended upland between valleys. The term is used in areas of both hill and mountain relief. HP rift valley – A valley that has developed along a long, narrow continental trough that has down-dropped and is bounded by normal faults; a graben of regional size. It marks part of a zone along which the entire thickness of the lithosphere has ruptured under crustal extension. SW & GG rill – A very small channel with steep sides caused by erosion and cut in unconsolidated materials by concentrated but intermittent flow of water, usually during and immediately following moderate rains or after ice / snow melt. Generally, a rill is not an obstacle to wheeled vehicles and is shallow enough (e.g., < 0.5 m) to be obliterated by ordinary tillage. Compare – gully. SW & GSST rim – The border, margin, edge, or face of a landform, such as the curved brim surrounding the top part of a crater or caldera; specifically the rimrock of a plateau or canyon. GG ripple mark – An undulating surface of alternating, subparallel, small-scale ridges and depressions, commonly composed of loose sand. It is produced on land by wind and under water by the agitation of water by currents or wave action, and generally tends at right angles or obliquely to the direction of flow of the moving fluid. Compare – giant ripple mark. GG rise – [soil survey] A general term for a slight increase in slope (e.g., d 3%) and elevation of the land surface, usually with a broad, low summit and gently sloping sides. The term is restricted to landforms and microfeatures in areas of very low relief such as lake plains or coastal plains. SW & GG rise – [geomorphology] A geomorphic component of flat plains (e.g., lake plain, low coastal plain, low-gradient till plain) consisting of a slightly elevated but low, broad area with low slope gradients (e.g., 1-3 % slopes); typically a microfeature but can be fairly extensive. Commonly soils on a rise are better drained than those on the surrounding talf. Compare – talf. SW riser – [geomorphology] A geomorphic component of terraces, flood-plain steps, and other stepped landforms consisting of the vertical or steep side slope (e.g., escarpment) typically of minimal aerial extent. Commonly a recurring part of a series of natural, step-like landforms such as successive stream terraces. Its characteristic shape and alluvial sediment composition are derived from the cut and fill processes of a fluvial system. Compare – tread. SW river – [streams] (a) A general term for a natural, freshwater surface stream of considerable volume and generally with a permanent base flow, moving in a defined channel toward a larger river, lake, or sea. (b) (not recommended: colloquial - New England, USA) A small watercourse which elsewhere in the USA is known as a creek. Compare – stream. GG river valley – an elongate depression of the Earth's surface carved by a river during the course of its development. Compare – valley side, valley floor. GG road bed – The trace or track of a wheeled vehicle route that may or may not be raised slightly above the adjacent land, and composed of earthy fill material (gravel, rock fragments, etc.) or local soil material. Traffic can alter various soil properties primarily by compaction. Abandoned or reclaimed beds may no longer be topographically or visually distinct. However, materials used to construct beds or changes in soil properties may continue to have a significant impact on soil management or plant growth. SW road cut – A common anthropogenic feature, typically a microfeature, consisting of the sloping, cut surface flanking a road bed on one or both sides, that remains after local topography is minimized by cutting an elongated depression through higher ground during road construction; a type of cutbank. Compare – cut, cutbank. SW roche moutonnée – A small elongate protruding knob or hillock of bedrock, so sculptured by a large glacier as to have its long axis oriented in the direction of ice movement, an upstream (stoss or scour) side that is gently inclined, smoothly rounded, and striated, and a downstream (lee or pluck) side that is steep and rough. It is usually a few meters in height, length, and breadth. GG rock anhydrite – A sedimentary rock (evaporite) composed chiefly of mineral anhydrite (anhydrous CaSO4); The rock is generally massive, cryptocrystalline, and may exhibit rhythmic sedimentation (rhymites). Compare – rock gypsum, rock halite. SW rockfall – The mass movement process, associated sediments (rockfall deposit), or resultant landform characterized by a very rapid type of fall dominated by downslope movement of detached rock bodies which fall salt marsh – Flat, poorly drained area that is subject to periodic or occasional overflow by salt water, containing water that is brackish to strongly saline, and usually covered with a thick mat of grassy halophytic plants; e.g., a coastal marsh periodically flooded by the sea, or an inland marsh, (or salina) in an arid region and subject to intermittent overflow by salty water. Compare – tidal marsh, mud flat. GG salt pond – A large or small body of salt water in a marsh or swamp along the seacoast. GG sand boil – An accumulation of sand commonly in the form of a low mound, produced by the expulsion of liquefied sand to the ground surface; sometimes called sand volcanoes (not preferred). Examples are found on top of some landslide deposits (i.e., spreads) or on the upper surface of highly contorted layers of laminated sediments. SW & GG sand dune – see dune. sandur – (not preferred) use outwash plain. sand flow – (a) A flow of wet sand, as along banks of noncohesive clean sand that is subject to scour and to repeated fluctuations in pore-water pressure due to rise and fall of the tide. (b) A flow of loose, dry sand, as along the slip face of a sand dune; typically a microfeature. SW, CV, & GG sandhills – A region of semi-stabilized sand dunes or sandy hills, either covered with vegetation or bare, as in north-central Nebraska and the midlands of the Carolinas. GG sand pit – A depression, ditch or pit excavated to furnish sand for roads or other construction purposes off-site; a type of borrow pit. SW sand plain – (a) [geomorphology] A sand-covered plain, which may originate by deflation of sand dunes, and whose lower limit of erosion is governed by the water table. Also spelled sandplain. GG. (b) [glacial geology] (not preferred – refer to sandy outwash plain) A small outwash plain composed chiefly of sand deposited by meltwater streams flowing from a glacier. GG sand ramp – A sand sheet blown up onto the lower slopes of a bedrock hill or mountain and forming an inclined plane, sometimes filling small mountain-side valleys and even crossing low passes. Compare – climbing dune, sand sheet. FFP & SW sand ridge – (a) (not preferred) An imprecise, generic name for any low ridge of sand, formed at some distance from shore, e.g., submerged (longshore bar) or emergent (barrier beach). (b) One of a series of long, wide, extremely low, parallel ridges believed to represent the eroded stumps of former longitudinal sand dunes, as in western Zimbabwe. GG sand sheet – A large, irregularly shaped, commonly thin, surficial mantle of eolian sand, lacking the discernible slip faces that are common on dunes. GG sand volcano – (not preferred) use sand boil. sand wedge – (not preferred) refer to ice wedge cast. sandstone – Sedimentary rock containing dominantly sand-size clastic particles. HP sanitary landfill – A land area where municipal solid waste is buried in a manner engineered to minimize environmental degradation. Commonly the waste is compacted and ultimately covered with soil or other earthy material. Compare – dump. GG saprolite – Soft, friable, isovolumetrically weathered bedrock that retains the fabric and structure of the parent rock (Colman and Dethier, 1986) and exhibiting extensive inter-crystal and intra-crystal weathering. In pedology, saprolite was formerly applied to any unconsolidated residual material underlying the soil and grading to hard bedrock below. Compare – grus, residuum. SW & HP scabland – An elevated, flat-lying, basalt-floored area, with little if any soil cover, sparse vegetation, and usually deep, dry channels scoured into the surface, especially by glacial meltwaters such as the Channeled Scablands of eastern Washington. Compare – coulee. GG scalped area – A modified slope, feature, or land area where much or all of the natural soil has been mechanically removed (e.g., scraped off) due to construction or other management practices. Compare – truncated soil. SW scarp – An escarpment, cliff, or steep slope of some extent along the margin of a plateau, mesa, terrace, or structural bench. A scarp may be of any height. Compare – escarpment. GG scarp slope – The relatively steeper face of a cuesta, facing in a direction opposite to the dip of the strata. Compare – dip slope. GG scoria – (a) [soils] Vesicular rock fragments e 2 mm in at least one dimension and a specific gravity > 2.0, or a cindery crust of such material on the surface of andesitic or basaltic lava; the vesicular nature is due to the escape of volcanic gases before solidification; it is usually heavier, darker, and more crystalline than pumice. Compare – cinders, pumice, tephra. (b) [geology] The same as (a) except no size restrictions are applied. SW scour – [geomorphology] The powerful and concentrated clearing and digging action of flowing air, water, or ice, especially the downward erosion by stream water in sweeping away mud and silt on the outside curve of a bend, or during the time of a flood; a process. GG scour and fill – [geomorphology] A process of alternate excavation and refilling of a channel, as by a stream or the tides; especially such a process occurring in time of flood, when the discharge and velocity of an aggrading stream are suddenly increased, causing the digging of new channels that become filled with sediment when the flood subsides. Compare – cut and fill. GG scour channel – A large, groove-like erosional feature in a stream bed swept (scoured) by running water, generally leaving a gravel bottom. GG scree – A collective term for an accumulation of coarse rock debris or a sheet of coarse debris mantling a slope. Scree is not a synonym of talus, as scree includes loose rock fragments on slopes without cliffs. Compare – talus, colluvium, mass movement. HP scree slope – A portion of a hillside or mountainslope mantled by scree and lacking an up-slope rockfall source (i.e., cliff). Compare – talus slope, scree, talus. SW scroll – (not preferred) refer to meander scroll. sea – (a) A large inland body of salt water (e.g., the Salton Sea, CA). (b) A geographic subdivision of an ocean (e.g., the South China Sea). Compare – gulf, ocean, salt pond. GG sea cliff – [coastal] A cliff or slope produced by wave erosion, situated at the seaward edge of the coast or the landward side of the wave-cut platform. It may vary from an inconspicuous slope to a high, steep escarpment. GG sediment – Material, both mineral and organic, that is in suspension, is being transported, or has been moved from its site of origin by water, wind, ice or mass-wasting and has come to rest on the earth's surface either above or below sea level. Sediment in a broad sense also includes materials precipitated from solution or emplaced by explosive volcanism, as well as organic remains; e.g., peat that has not been subject to appreciable transport. HP sedimentary peat – An accumulation of organic material that is predominantly the remains of floating aquatic plants (e.g., algae) and the remains and fecal material of aquatic animals, including coprogenous earth. Compare – herbaceous peat, moss peat, woody peat, peat, muck, and mucky peat. SSM sedimentary rock – A consolidated deposit of clastic particles, chemical precipitates, or organic remains accumulated at or near the surface of the earth under "normal" low temperature and pressure conditions. Sedimentary rocks include consolidated equivalents of alluvium, colluvium, drift, and eolian, lacustrine, marine deposits; e.g., sandstone, siltstone, mudstone, claystone, shale, conglomerate, limestone, dolomite, and coal. Compare – sediment. HP seep – (noun) An area, generally small, where water outflows slowly at the land surface. Flow rates for seeps are too small to be considered as springs, but reflow and / or lateral subsurface flow keeps the surface or near soil saturated during dry periods. SW & GG seif dune – A large, sharp-crested, elongated, longitudinal (linear) dune or chain of sand dunes, oriented parallel, rather than transverse (perpendicular), to the prevailing wind. If unmodified, the crest, in profile, commonly consists of a succession of curved slip faces produced by strong, but infrequent cross winds. A seif dune may be as much as 200 m high and from 400 m to more than 100 km long. Compare – longitudinal dune. GG & HP semi-bolson – (colloquial: western USA) A wide desert basin or valley that is drained by an intermittent stream, an externally drained (open) intermontane basin. Compare – bolson. GG semi-open depression – A topographically enclosed basin that generally functions as a closed depression and lacks a defined exit channel. Surface water loss may occur via overland flow through a topographic low area or gap in response to large storm events. Semi-open depressions commonly contain small lakes, ponds, or wet meadows dominated by hydric soils (e.g., in karst valleys, or in low areas on marine terraces with < 1 % slopes). SW sewage lagoon – Any artificial pond or other water-filled excavation for the natural oxidation of sewage or disposal of animal manure. GG shale – Sedimentary rock formed by induration of a clay, silty clay, or silty clay loam deposit and having the tendency to split into thin layers, i.e., fissility. HP sheep tracks – (not recommended) use terracettes. shield volcano – A volcano having the shape of a very broad, gently sloping dome, built by flows of very fluid basaltic lava or rhyolitic ash flows. Compare – stratovolcano. GG & MA shoal – (noun) (a) A relatively shallow place in a stream, lake, sea, or other body of water; a shallows. (b) A natural, subaqueous ridge, bank, or bar consisting of, or covered by, sand or other unconsolidated material, rising from the bed of a body of water (e.g., estuarine floor) to near the surface. It may be exposed at low water. Compare – reef. SSS & GG slope wash – A collective term for non-fluvial, incipient alluvial processes (e.g., overland flow, minor rills) that detach, transport, and deposit sediments down hill and mountain slopes. Related sediments (slope alluvium) exhibit nominal sorting or rounding of particles, peds, etc., and lateral sorting downslope on long slopes; stratification is crude and intermittent and readily destroyed by pedoturbation and frost action. Also called slope wash processes. Compare – slope alluvium, colluvium, valley-side alluvium. SW slot canyon – A long, narrow, deep and tortuous channel or drainageway with sheer rock walls eroded into sandstone or other sedimentary rocks, especially in the semiarid western USA (e.g., Colorado Plateau); subject to flash flood events; depth to width ratios exceed 10:1 over most of its length and can approach 100:1; commonly containing unique ecological communities distinct from the adjacent, drier uplands. SW slough – (a) A small marsh, especially a marshy area lying in a local, shallow, closed depression on a piece of dry land, as on the prairie of the Midwestern USA. (b) A term used, especially in the Mississippi Valley, for a creek or sluggish body of water in a tidal flat, flood plain, or coastal marshland. Compare – bayou, oxbow. (c) A sluggish channel of water, such as a side channel of a river, in which water flows slowly through low, swampy ground, as along the Columbia River, or a section of an abandoned river channel which may contain stagnant water and occurs in a flood plain or delta. (d) (not preferred) An area of soft, miry, muddy or waterlogged ground, a place of deep mud. GG sloughed till – (not recommended) use flow till. slump – (not recommended: obsolete) refer to rotational slide. slump block – A mass of material torn away as a coherent unit during a landslide; a largely intact but displaced and commonly reoriented body of rock or soil. SW & GG slump till – (not recommended) use flow till. snowfield – (a) A broad expanse of terrain covered with snow, relatively smooth and uniform in appearance, occurring usually at high latitudes or in mountainous regions above the snowline and persisting throughout year. (b) A region of permanent snow cover, as at the head of a glacier; the accumulation area of a glacier. Compare – glacier. GG soil creep – (not preferred) refer to creep. soil fall – The mass movement process, associated sediments (soil fall deposit), or resultant landform characterized by a rapid type of fall involving the relatively free, downslope movement or collapse of detached, unconsolidated soil material which falls freely through the air (lacks an underlying slip face); sediments predominantly fine earth (< 2 mm); common along undercut stream banks. Also called earth fall and (not recommended) debris fall. Compare – rockfall, debris fall, topple, landslide. SW soil ripples – (not recommended) use terracettes. solifluction – Slow, viscous downslope flow of water-saturated regolith. Rates of flow vary widely. The presence of frozen substrate or even freezing and thawing is not implied in the original definition. However, one component of solifluction can be creep of frozen ground. The term is commonly applied to processes operating in both seasonal frost and permafrost areas. Compare – creep. NRC solifluction deposit – A deposit of nonsorted, water-saturated, earthy material locally derived that is moving or has moved down slope en masse, caused by the melting of seasonal frost or permafrost, resulting in an over- thickened leading edge of linear, lobate, or irregular forms that loosely parallel or obliquely follow the slope contour; may be surficially armored by rock fragments on the leading edge. SW solifluction lobe – An isolated tongue-shaped feature up to 25 m wide and 150 m or more long, formed by rapid solifluction on certain sections of a slope showing variations in gradient. This feature commonly has a steep (e.g., 15°- 60°) front and a relatively smooth upper surface. NRC solifluction sheet – A broad deposit of nonsorted, water-saturated, locally derived material that is moving or has moved downslope, en masse. Stripes are commonly associated with solifluction sheets. Compare – stripe. NRC solifluction terrace – A low step with a straight or lobate front, the latter reflecting local differences in rate of flow. A solifluction terrace may have bare mineral soil on the upslope part and 'folded under' organic matter in both the seasonally thawed and the frozen soil. NRC solution chimney – Small diameter (e.g., 1-5 m), irregular, hollow, vertical shaft 5-10+ m deep on karst landscapes, typically covered with a thin layer of soil or plant debris that can collapse and expose the shaft to the surface; represents a significant safety hazard. Locally called “stove-pipe sinkholes” in Florida (not recommended). Compare – solution pipe. SW solution corridor – A straight, open trench about 3 to 10 m wide in a karst area, formed by vertical and lateral solution zones developed along bedrock fractures; also called (not preferred) bogaz, zanjon (Puerto Rico). Compare – cutter, solution fissure, karst valley. SW & GG solution fissure – One of a series of vertical open cracks commonly < 0.5 m wide dissolved along joints or fractures, separating limestone pavement (pavement karst) into blocks (clints); also called kluftkarren (not preferred). Compare – cutter, solution corridor, karren. SW, GG, & WW solution pipe – A subsurface, vertical, cylindrical or cone-shaped hole, formed by dissolution in soluble bedrock (e.g., limestone) and often without surface expression, that is filled with detrital material (e.g., soil) and which serves as a bypass route for internal water flow. SW & GG solution platform – A broad, nearly horizontal intertidal surface (modern or relict) formed across carbonate rocks, produced primarily by solution with contributions by intertidal weathering and biological erosion and deposition, not by abrasion. Compare – wave-cut platform. SW & GG solution sinkhole – The most common type of sinkhole, caused by dissolution that forms fissures or a chimney and a depression in the bedrock surface which grows when closely spaced fissures underneath it enlarge and coalesce. Compare – collapse sinkhole. SW, WW, & GG solution valley – (not preferred) use karst valley. sorted circle – A type of patterned ground whose mesh (shape) is largely circular and has a sorted appearance commonly due to a border of rock fragments surrounding finer material, occurring either singly or in groups. Diameters range from a few centimeters to more than 10 meters. The rock fragment border may be 35 cm high and 8 to 12 cm wide. Compare – patterned ground. GG and NRC sorted polygon – refer to patterned ground. sound – (a) A relatively long, narrow waterway connecting two larger bodies of water (as a sea or lake with the ocean or another sea) or two parts of the same water body, or an arm of the sea forming a channel between the mainland and an island (e.g., Puget Sound, WA); it is generally wider and more extensive than a strait [coast]. (b) A long, large, rather broad inlet of the ocean, generally extending parallel to the coast (e.g., Long Island Sound, NY). (c) A lagoon along the southeast coast of the USA (e.g., Pamlico Sound, NC). (d) A long bay or arm of a lake; a stretch of water between the mainland and a long island in a lake. Compare – sound, lagoon, gulf, ocean. GG spatter cone – A small, steep-sided cone (e.g., 3 to 15 m high, or more) built up on a lava flow, usually pahoehoe, composed of clots of lava ejected with escaping gases from a vent or fissure which spatters and congeals as it hits the ground to form a small cone; rougher lava clots than a spiracle. Compare – spiracle. SW specific gravity – The ratio of a material’s density to that of water [material weight in air ÷ (weight in air - weight in water)]. Used to differentiate different kinds of volcaniclastics and other materials. SW spiracle – [volcanic] A small tubular opening or chimney formed by fluid lava congealing and mounding around a fumarolic vent in a basaltic lava flow, usually about 1 m in diameter and up to 5 m high, although in the northwestern USA where spiracles are common they generally are 10 m in diameter and 12 m high or more; formed by a gaseous explosion in lava that is still fluid, probably due to steam generated from underlying wet material; smoother lava clots and drapes than a spatter cone. Compare – spatter cone. SW, GS, & GG spit – (a) A small point or low tongue or narrow embankment of land, commonly consisting of sand or gravel deposited by longshore transport and having one end attached to the mainland and the other terminating in open water, usually the sea; a finger-like extension of the beach. (b) A relatively long, narrow shoal or reef extending from the shore into a body of water. GG splay – (not preferred) refer to flood-plain splay. spoil bank – A bank, mound, or other artificial accumulation of rock debris and earthy dump deposits removed from ditches, strip mines, or other excavations. Compare – dredge spoil bank. SW spoil pile – (a) A bank, mound, or other artificial accumulation composed of spoil; e.g., an embankment of earthy material removed from a ditch and deposited alongside it. Compare – dredge spoil bank. (b) A pile of refuse material from an excavation or mining operation; e.g., a pile of dirt removed from, and stacked at the surface of a mine in a conical heap or in layers. SW & GG sporadic permafrost – The area near the southern boundary of discontinuous permafrost where permafrost occurs in isolated patches or islands. Compare – continuous permafrost, discontinuous permafrost. NRC spread – see lateral spread. spur – [geomorphology] A subordinate ridge or lesser elevation that projects sharply from the crest or side of a hill, mountain, or other prominent range of hills or mountains. GG spur ridge – (not recommended) use spur. stack [coast] – An isolated pillar-like rocky island or mass near a cliffy shore, detached from a headland by wave erosion assisted by weathering; especially one showing columnar structure with horizontal stratification. Examples occur along the Oregon coast and the Lake Superior shore. SW & GG stack [geom.] – A steep-sided mass of rock rising above its surroundings on all sides from a slope or hill. Compare – knob. GG stagnant ice – (a) Glacial ice that is not flowing forward and is not receiving material from an accumulation area. (b) Detached blocks of ice left behind by a retreating glacier, usually buried in a moraine and melting very slowly. GG structural bench – A shelf or step-like landform produced or controlled by erosion resistant, horizontally- bedded rock. Erosion removes overlying weaker rock or sediment forming a nearly level to gently inclined surface that rests on a relatively resistant strata or rock that ascends to a higher slope or platform. Structural benches may occur as a single feature or as a series of stepped-surfaces where alternating weak and resistant strata exist. Due to erosion resistance, structural benches may have little or no geomorphic implication regarding fluvial deposition, past erosion cycles or former stream, basin, or base levels. Compare – mesa, pediment, ledge; see scarp. SW subaerial – (adjective) Said of conditions and processes, such as erosion, that exist or operate in the open air on or immediately adjacent to the land surface; or of features and materials, such as eolian deposits, that are formed or situated on the land surface. Compare – subaqueous. GG subaqueous – (adjective) Said of conditions and processes, features or deposits, that exist or operate in or under water. Compare – subaerial. SSS & GG subaqueous landscapes – Permanently submerged areas that are fundamentally the same as subaerial (terrestrial) systems in that they have a discernable topography composed of mappable, subaqueous landforms. SSS subaqueous soil – Soil that forms in sediment found in shallow, permanently flooded environments. Excluded from the definition of these soils are any areas “permanently covered by water too deep (typically greater than 2.5 m) for the growth of rooted plants.” SSS subglacial – (a) Formed or accumulated in or by the bottom parts of a glacier or ice sheet; said of meltwater streams, till, moraine, etc. (b) Pertaining to the area immediately beneath a glacier, as subglacial eruption or subglacial drainage. GG subglacial flow till – refer to flow till. subglacial melt-out till – refer to melt-out till. subglacial till – Till deposited beneath, in, or by the bottom part of a glacier or ice sheet; subglacial till types include lodgment till, subglacial flow till, and subglacial melt-out till. Compare – till and supraglacial till. SW & GM submerged back-barrier beach – A permanently submerged extension of the back-barrier beach that generally parallels the boundary between estuary and the barrier island. Compare – submerged mainland beach, barrier beach. SSS submerged mainland beach – A permanently submerged extension of the mainland beach that generally parallels the boundary between an estuary or lagoon and the mainland. Compare – submerged back-barrier beach, barrier beach. SSS submerged point bar [coast] – The submerged extension of an exposed (subaerial) point bar. SSS submerged wave-built terrace – A subaqueous, relict depositional landform originally constructed by river or longshore sediment deposits along the outer edge of a wave-cut platform and later submerged by rising sea level or subsiding land surface. Compare wave – built terrace, wave-cut platform. GG submerged wave-cut platform – A subaqueous, relict erosional landform that originally formed as a wave-cut bench and abrasion platform from coastal wave erosion and later submerged by rising sea level or subsiding land surface. Compare – wave-built terrace, wave-cut platform. GG submerged-upland soil – Mineral or organic soil that primarily formed in a subaerial setting but is now under water, commonly in intertidal or subaqueous settings. Inundation could occur for various reasons (e.g., sea-level rise in a marine or estuarine system or ponding from a dam). In intertidal settings, tidal marsh soils may occur above former subaerial soils (see submerged-upland tidal marsh). In subaqueous settings (permanently submerged), submerged-upland soils typically occur below a cap of subaqueous soil forming in the subaqueous environment. SW submerged-upland tidal marsh – An extensive nearly level, intertidal landform composed of unconsolidated sediments (clays, silts, and/or sand and organic materials), a resistant root mat, vegetated dominantly by hydrophytic (water loving) plants. The mineral sediments largely retain pedogenic horizonation and morphology (e.g., argillic horizons) developed under subaerial conditions prior to submergence due to sea level rise; a type of tidal marsh. Compare – tidal marsh. SW subtidal – (adjective) Continuous submergence of substrate in an estuarine or marine ecosystem; these areas are below the mean low tide. Compare – intertidal. SSS & CC subtidal wetlands – Permanently inundated areas within estuaries dominated by subaqueous soils and submerged aquatic vegetation. SSS summit – (a) The topographically highest position of a hillslope profile with a nearly level (planar or only slightly convex) surface. Compare – shoulder, backslope, footslope, and toeslope, crest. (b) A general term for the top, or highest area of a landform such as a hill, mountain, or tableland. It usually refers to a high interfluve area of relatively gentle slope that is flanked by steeper slopes, e.g., mountain fronts or tableland escarpments. HP superglacial – (not recommended) refer to supraglacial. supraglacial – Carried upon, deposited from, or pertaining to the top surface of a glacier or ice sheet; said of meltwater streams, till, drift, etc. GG supraglacial debris-flow sediment – (not preferred) refer to till. supraglacial flow till – refer to flow till. supraglacial melt-out till – refer to melt-out till. supraglacial till – Till deposited on top of or within the upper part of a glacier or ice sheet. Melting of glacial ice deposits supraglacial till atop subjacent material, which forms topographic highs on a resultant landscape. Supraglacial till types include supraglacial flow till and supraglacial melt-out till. Compare – till and subglacial till. SW & GM. surface mine – A depression, open to the sky, resulting from the surface extraction of earthy material (e.g., soil / fill) or bedrock material (e.g., coal). Compare – borrow pit, openpit mine, quarry. SW swale – (a) A shallow, open depression in unconsolidated materials which lacks a defined channel but can funnel overland or subsurface flow into a drainageway. Soils in swales tend to be moister and thicker (cumulic) compared to surrounding soils. SW. (b) A small, shallow, typically closed depression in an undulating ground moraine formed by uneven glacial deposition; Compare – swell-and-swale topography. (c) (not preferred; refer to interdune) A long, narrow, generally shallow, trough-like depression between two beach ridges, and aligned roughly parallel to the coastline. GG swallow hole – A closed depression or doline into which all or part of a stream disappears underground. GG swamp – An area of low, saturated ground, intermittently or permanently covered with water, and predominantly vegetated by shrubs and trees, with or without the accumulation of peat. Compare – marsh, bog, fen. GG swash zone – The sloping part of the beach that is alternately covered and uncovered by the uprush of waves, and where longshore movement of water occurs in a zigzag (upslope-downslope) manner. Compare – shoreline. GG swell – (not recommended) refer to swell-and-swale topography. swell and swale topography – A local scale topography composed of small, well-rounded hillocks and shallow, closed depressions irregularly spaced across low-relief ground moraine (slopes generally 2 – 6%); the effect is a subdued, irregularly undulating surface that is common on ground moraines. Micro-elevational differences generally range from < 1 to < 5 m. SW syncline – (a) [landform] A unit of folded strata that is concave upward whose core contains the stratigraphically younger rocks, and occurs at the earth’s surface. In a single syncline, beds forming the opposing limbs of the fold dip toward its axial plane. Compare – monocline, syncline, fold. SW & HP. (b) [structural geology] A fold, at any depth, generally concave upward whose core contains the stratigraphically younger rocks. GG tableland – A general term for a broad upland mass with nearly level or undulating summit area of large extent and steep side slopes descending to surrounding lowlands (e.g., a large plateau). Compare – plateau, mesa, cuesta. HP talf – [geomorphology] A geomorphic component of flat plains (e.g., lake plain, low coastal plain, low-gradient till plain) consisting of an essentially flat (e.g., 0-1 % slopes) and broad area dominated by closed depressions and a non-integrated or poorly integrated drainage system. Precipitation tends to pond locally and lateral transport is slow both above and below ground, which favors the accumulation of soil organic matter and a retention of fine earth sediments; better drained soils are commonly adjacent to drainageways. Compare – rise. SW talus – Rock fragments of any size or shape (usually coarse and angular) derived from and lying at the base of a cliff or very steep rock slope. The accumulated mass of such loose broken rock formed chiefly by falling, rolling, or sliding. Compare – talus slope, colluvium, mass movement, scree. GG talus cone – A steep (e.g., 30 - 40º), cone-shaped landform at the base of a cliff or escarpment that heads in a relatively small declivity or ravine, and composed of poorly sorted rock and soil debris that has accumulated primarily by episodic rockfall or, to a lesser degree, by slope wash. Finest material tends to be concentrated at the apex of the cone. Not to be confused with an alluvial cone; a similar feature but of fluvial origin, composed of better stratified and more sorted material, and that tapers up into a more extensive drainageway. Compare – alluvial cone, beveled base, talus slope. SW talus slope – a portion of a hillslope or mountainslope mantled by talus and lying below a rockfall source (e.g., cliff). Compare – scree slope, scree, talus. Compare – beveled base. SW tank – (colloquial: southwestern USA) A natural depression or cavity in impervious rocks in which water collects and remains for the greater part of the year. GG tarn – A relatively deep, steep-banked lake or pool occupying an ice-gouged rock basin amid glaciated mountains. A cirque lake. GG tephra – A collective, general term for any and all clastic materials, regardless of size or composition, ejected from a vent during a volcanic eruption and transported through the air; including ash [volcanic; < 2 mm], blocks topography – The relative position and elevations of the natural or manmade features of an area that describe the configuration of its surface. HP topple – A category of mass movement processes, associated sediments (topple deposit), or resultant landform characterized by a localized, very rapid type of fall in which large blocks of soil or rock literally fall over, rotating outward over a low pivot point. Portions of the original material may remain intact, although reoriented, within the resulting debris pile. Types of topples can be specified based on the dominant particle size of sediments (i.e., debris topple, soil topple, rock topple. Compare – fall, flow, slide, spread, complex landslide, landslide. SW & DV tor – A high, isolated pinnacle, or rocky peak; or a pile of rocks, much-jointed and usually granitic, exposed to intense weathering, and often assuming peculiar or fantastic shapes. GG Toreva block – A slump block consisting of a single large mass of unjostled material which, during descent, has undergone a backward rotation toward the parent cliff along a horizontal axis that roughly parallels it; a type of rotational landslide. The unit forms a crude, elongated rectangular block rather than a bowl shape or chaotic mass; typically associated with horizontal to gently dipping sequence of coherent bedrock such as sandstone, which overlies a less coherent bedrock formation such as clay shale which is prone to slumping (e.g., southern Black Mesa area, AZ). SW, GG, & RF tower karst – (a) A type of tropical karst topography characterized by isolated, steep-sided, residual limestone hills or ridges with vertical or near-vertical walls, and may be relatively flat-topped; commonly surrounded by a flat alluvial plain or lagoons. (Also called fenglin). (b) A cluster of peaks or ridges with vertical or near-vertical walls, and convex upper side slopes where towers rise from a common base and are separated by deep, rugged ravines or large sinkholes. (Also called fengcong, turmkarst). Compare – karst tower, cockpit karst, cone karst, fluviokarst, kegel karst, sinkhole karst. SW & GG translational debris slide – The mass movement process, associated sediments (translational debris slide deposit), or resultant landform characterized by an extremely slow to moderately rapid type of slide, composed of comparatively dry and largely unconsolidated earthy material, portions or blocks of which remain largely intact and in which movement occurs along a well-defined, planar slip face roughly parallel to the ground surface and resulting in lateral displacement but no rotation of the displaced mass; sediments have substantial proportions of both fine earth and rock fragments. The landform may be single, successive (repeated up and down slope), or multiple (as the number of slide components increase). Compare – translational earth slide, translational rock slide, rotational slide lateral spread, landslide. SW & DV translational earth slide – The mass movement process, associated sediments (translational earth slide deposit), or resultant landform characterized by an extremely slow to moderately rapid type of slide, composed of comparatively dry and largely unconsolidated earthy material, portions or blocks of which remain largely intact and in which movement occurs along a well-defined, planar slip face roughly parallel to the ground surface and resulting in lateral displacement but no rotation of the displaced mass; sediments predominantly fine earth (< 2 mm). The landform may be single, successive (repeated up and down slope), or multiple (as the number of slide components increase). Compare translational debris slide, translational rock slide, rotational slide, lateral spread, landslide. SW & DV translational rock slide – The mass movement process, associated sediments (translational rock slide deposit), or resultant landform characterized by an extremely slow to moderately rapid type of slide, composed of comparatively dry and largely consolidated rock bodies, portions or blocks of which remain largely intact and in which movement occurs along a well-defined, planar slip face roughly parallel to the ground surface and resulting in lateral displacement but no rotation of the displaced mass; sediments predominantly fine earth (< 2 mm). The landform may be single, successive (repeated up and down slope), or multiple (as the number of slide components increase). Compare translational debris slide, translational earth slide, rotational slide, lateral spread, landslide. SW & DV translational slide – A category of mass movement processes, associated sediments (translational slide deposit), or resultant landform characterized by the extremely slow to moderately rapid downslope displacement of comparatively dry soil-rock material on a surface (slip face) that is roughly parallel to the general ground surface, in contrast to falls, topples, and rotational slides. The term includes such diverse slide types as translational debris slides, translational earth slide, translational rock slide, block glides, and slab or flake slides. Compare – rotational slide, slide, landslide. SW, DV, & GG transverse dune – A very asymmetric sand dune elongated perpendicular to the prevailing wind direction, having a gentle windward slope and a steep leeward slope standing at or near the angle of repose of sand; it generally forms in areas of sparse vegetation. Compare – longitudinal dune. GG tread – [geomorphology] A geomorphic component of terraces, flood-plain steps, and other stepped landforms consisting of the flat to gently sloping, topmost and laterally extensive slope. Commonly a recurring part of a series of natural, step-like landforms such as successive stream terraces. Its characteristic shape and alluvial sediment composition is derived from the cut and fill processes of a fluvial system. Compare – riser. SW tree-throw – (not preferred) see tree-tip, tree-tip mound, tree-tip pit. tree-tip – The process of uprooting and tipping over of trees by strong winds, commonly resulting in a small depression from which the root-ball is displaced and an adjacent mound from the sediments subsequently sloughed from the root ball. Most prevalent in shallow forested soils over a restrictive layer (e.g., bedrock); also called tree-throw, windthrow. Compare – tree-tip mound, tree-tip pit. SW tree-tip mound – The small mound of debris sloughed from the root plate (root ball) of a tipped-over tree. Sometimes called a cradle knoll (not recommended). Local soil horizons are commonly obliterated and result in heterogeneous strata. Compare – tree-tip pit. SW & BHM tree-tip pit – The small pit or depression resulting from an area vacated by the root plate (ball) resulting from tree-tip ("tree-throw"). Such pits are commonly adjacent to small mounds composed of the displaced material. Subsequent infilling commonly results in a heterogeneous soil matrix that may or may not include a stone line that lines the depression. Compare – tree-tip mound. SW & BHM tree-tip pit and mound topography – A local-scale topography composed of irregularly spaced, small, closed depressions and adjacent mounds caused by the displacement of root balls from trees knocked down by wind (i.e., tree-tip; also called tree-throw). The result is a subdued, irregularly pock-marked or undulating surface; most common in forested areas overlying shallow rooting conditions (e.g., lithic contact, water table, etc). Micro-elevational differences generally range from 0.5 to < 2 m. Sometimes also referred to as (not preferred:) cradle and knoll or pit and mound topography. Compare – tree-tip mound, tree-tip pit. SW trellis drainage pattern – A drainage pattern characterized by parallel main streams intersected at, or nearly at, right angles by their tributaries, which in turn are fed by elongated secondary tributaries and short gullies parallel to the main streams, resembling, in plan view, the stems of a vine on a trellis. This pattern indicates marked bedrock structural control rather than a type of bedrock and usually indicates in which the main parallel channels follow the strike of the beds. It is commonly developed where the beveled edges of alternating hard and soft rocks outcrop in parallel belts, as in titled, interbedded sedimentary rocks in a rejuvenated folded-mountain region or in a maturely dissected belted coastal plain of tilted strata. SW, GG, & WA tripoli – A light-colored, porous, friable, siliceous (largely chalcedonic) sedimentary rock, which occurs in powdery or earthy masses that result from the weathering of siliceous limestone. It has a harsh, rough feel and is used to polish metals and stones. GG trough – [geomorphology] (a) Any long, narrow depression in the earth's surface, such as one between hills or with no surface outlet for drainage. (b) (not preferred – see U-shaped valley, mountain valley) A broad, elongate U-shaped valley, such as a glacial trough. Compare – U-shaped valley. GG trough bottom – (not preferred) refer to glacial-valley floor. trough end – (not recommended: refer to cirque, cove). The steep, semicircular rock wall forming the abrupt head or end of a U-shaped valley. Compare – headwall. GG trough valley – (not preferred) refer to U-shaped valley. trough wall – (not preferred) refer to glacial-valley wall. truncated soil – Soil that has had part or all of the upper soil horizon(s) removed by erosion, excavation, etc., but retains some portion of the original subsoil horizons intact. Compare – scalped area. SW & GSST tuff – A generic term for any consolidated or cemented deposit that is ≥ 50 percent volcanic ash (< 2 mm); various types of tuff can be recognized based on composition: acidic tuff is predominantly composed of acidic particles; basic tuff is predominantly composed of basic particles. SW tumulus – (pl. tumuli) A small dome or mound on the surface of a lava flow formed by the buckling of the congealing crust near the edge of a flow caused by differences in flow rates of the cooler crust above and the hotter, more fluid lava below. Dimensions commonly range from < 1 m to 5 m in height, 3 to 10 m in width and 30 to 40 m in length. Some tumuli are hollow. Compare – volcanic pressure ridge. SW, GG, & GS tunnel valley – A relatively shallow trench or depression cut into drift and other loose material, or in bedrock, by a subglacial stream not loaded with coarse sediment that may or may not be part of the present day drainage pattern. GG tunnel-valley lake – A glacial lake occupying a portion of a tunnel valley. GG turf hummock – A hummock consisting of vegetation and organic matter with or without a core of mineral soil or stones (typically 10-50 cm height; 20-90 cm diameter). Groups of hummocks can form a type of patterned ground common to tundra or wet areas (e.g., marsh). Compare – earth hummock, nonsorted circle, patterned ground. NRC & SW unconformity – A substantial break or gap in the geologic record where a unit is overlain by another that is not in stratigraphic succession. Compare – conformity, discontinuity. GG underfit stream – A stream that appears to be too small to have eroded the valley in which it flows; a stream whose volume is greatly reduced or whose meanders show a pronounced shrinkage in radius. It is a common result of drainage changes effected by capture, glaciers, or climatic variations. GG upland – [geomorphology] An informal, general term for (a) the higher ground of a region, in contrast with a low-lying, adjacent land such as a valley or plain. (b) Land at a higher elevation than the flood plain or low stream terrace; land above the footslope zone of the hillslope continuum. Compare – lowland. HP & GG volcaniclastic – (adjective) Pertaining to the entire spectrum of fragmental materials with a preponderance of clasts of volcanic origin. The term includes not only pyroclastic materials but also epiclastic deposits derived from volcanic source areas by normal processes of mass movement and stream erosion. Examples: welded tuff, volcanic breccia, lahar deposit. HP volcano – (a) A vent in the surface of the Earth through which magma and associated gases and ash erupt; also, the form or structure, usually conical, that is produced by the ejected material. (b) Any eruption of material, e.g., mud, sand, etc. that resembles a magmatic volcano. GG V-shaped valley – A valley having a pronounced cross profile suggesting the form of the letter "V", characterized by steep sides and short tributaries; specifically a narrow valley resulting from downcutting by a stream. The "V" becomes broader as the downcutting progresses. Compare – U-shaped valley. GG wash – (dry wash) (colloquial: western USA) The broad, flat-floored channel of an ephemeral stream, commonly with very steep to vertical banks cut in alluvium. Note: When channels reach intersect zones of ground-water discharge they are more properly classed as "intermittent stream" channels. Synonym - arroyo. Compare – gully. HP washover fan – A fan-like deposit of sand washed over a barrier island or spit during a storm and deposited on the landward side. Washover fans can be small to medium sized and completely subaerial, or they can be quite large and include subaqueous margins extending into adjacent lagoons or estuaries. Large fans can be subdivided into sequential parts: ephemeral washover channel (microfeature) cut through dunes or beach ridges, back-barrier flats, (subaqueous) washover-fan flat, (subaqueous) washover-fan slope. Subaerial portions can range from barren to completely vegetated. SSS washover-fan apron – (not preferred) use washover-fan flat. washover-fan flat – A gently sloping, fan-like, subaqueous landform created by overwash from storm surges that transports sediment from the seaward side to the landward side of a barrier island (GG). Sediment is carried through temporary overwash channels that cut through the dune complex on the barrier spit (Fisher and Simpson, 1979; Boothroyd et al., 1985; Davis, 1994) and spill out onto the lagoon-side platform where they coalesce to form a broad belt. Also called storm-surge platform flat (Boothroyd et al., 1985) and washover fan apron (GG). Compare – washover fan slope. SSS washover-fan slope – A subaqueous extension of a washover-fan flat that slopes toward deeper water of a lagoon or estuary and away from the washover-fan flat. Compare – washover-fan flat. SSS water – [soil survey] A generic map unit for any permanent, open body of water (pond, lake, reservoir, etc.) that does not support rooted plants. SW water-lain moraine – A terminal, end, or recessional moraine formed subaqueously by a glacier that terminated in a water body (e.g., glacial lake, sea, or ocean). A water-lain moraine may occur at the present land surface as a result of isostatic rebound or lake drainage. Compared to a land-based moraine of similar origin, a water-lain moraine displays sediment (till) modification by wave and/or current action and has a somewhat subdued topography. SW waterway – (a) A general term for a way or channel, either natural (as a river) or artificial (as a canal), for conducting the flow of water. (b) A navigable body or stretch of water available for passage; a watercourse. Compare – drainageway. GG wave-built terrace – A gently sloping coastal feature at the seaward or lakeward edge of a wave-cut platform, constructed by sediment brought by rivers or drifted along the shore or across the platform and deposited in the deeper water beyond. Compare – submerged wave-built terrace, beach plain, strand plain. GG wave-cut platform – A gently sloping surface produced by wave erosion, extending into the sea or lake from the base of the wave-cut cliff. This feature represents both the wave-cut bench and the abrasion platform. Compare – submerged wave-cut platform. GG wave-cut terrace – (not recommended) use wave-built terrace. wave-worked till plain – A glaciated land area that has the characteristics of a till plain, but that was also inundated by a glacial lake. The area possesses a gently undulating till-topography rather than a distinctive, low- relief lake plain surface. Lacustrine sediments, however, are absent or occur only sparsely, but a wave/current- modified, surficial mantle may commonly exist atop the till. Topographic highs, which were once islands, may possess shore features (e.g., wave-cut scarps, strandlines, beach deposits). Compare – till–floored lake plain. SW weathering – All physical disintegration, chemical decomposition, and biologically induced changes in rocks or other deposits at or near the earth's surface by atmospheric or biologic agents or circulating surface waters with essentially no transport of the altered material. These changes result in disintegration and decomposition of the material. Compare – regolith, residuum, saprolite. HP welded soil – (not preferred) use overprinted soil. welded tuff – A glass-rich, pyroclastic rock composed of volcanic ash indurated at the time of deposition by the welding together of its glass shards under the combined action of the heat retained by particles, the weight of overlying material, and hot gasses. It is generally composed of silica pyroclasts and appears banded or streaked. GG welding – (a) Consolidation of sediments (especially of clays) by pressure resulting from the weight of superincumbent material or from earth movement, characterized by cohering particles brought within the limits of mutual molecular attraction as water is squeezed out of the sediments. (b) the diagenetic process whereby discrete crystals and/or grains become attached to each other during compaction, often involving pressure solution and pressure transfer. GG wind gap – A former water gap now abandoned by the stream that formed it, suggesting stream piracy or stream diversion. HP window – [tectonic] An eroded area of a thrust sheet, commonly a basin or valley floor, that exposes the incongruous bedrock stratigraphy beneath the thrust-sheet; a particular structural or stratigraphic relationship is implied, rather than a particular topographic form. Common in the Appalachian and Rocky Mountain margins. Synonym: fenster. GG, WT, & SW windthrow – (not preferred) see tree-tip. wind-tidal flat – A broad, low-lying, nearly-level sand flat that is alternately inundated by ponded rainwater or by wind-driven bay or estuarine water from storm surges or seiche. Frequent salinity fluctuations and prolonged periods of subaerial exposure preclude establishment of most types of vegetation except for mats of filamentous blue-green algae. Compare – tidal flat. SSS & HF woody organic materials – see organic materials. woody peat – An accumulation of organic material that is predominantly composed of trees, shrubs, and other woody plants. Compare herbaceous peat, moss peat, sedimentary peat, peat, muck, and mucky peat. SSM yardang – (a) A microfeature in the form of a long, irregular, sharp-crested, undercut ridge between two round- bottomed troughs, carved on a plateau or unsheltered plain in a desert region by wind erosion, and cut into soft but coherent deposits (such as clayey sand); it lies in the direction of the dominant wind, and may be up to 6 m high and 40 m wide. (b) A landform produced in a region of limestone or sandstone by infrequent rains combined with wind action, and characterized by “a surface bristling with a fine lacework of sharp ridges pitted by corrosion”. Compare – pavement karst. GG yardang trough – A long, shallow, round-bottomed groove, furrow, trough, or corridor excavated in the desert floor by wind abrasion, and separating two yardangs. Compare – yardang. GG zibar – A small, low-relief sand dune that lacks discernible slip faces and commonly occurs on sand sheets, in interdune areas, or in corridors between larger dunes. Zibar spacing can range from 50 to 400 m with local relief of less than 10 m. Unlike coppice dunes, zibars are not related to deposition around vegetation. Generally dominated by coarser sands. Compare – dune, coppice dune. SW, GG, NL, & CW