Glacial Landforms and Processes: Terms and Definitions, Quizzes of Engineering

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TERM 1 Horn DEFINITION 1 peak flanked by 3 or more cirques TERM 2 Cirque DEFINITION 2 scooped out bowls on mountain peaks at heads of valley glaciers (north and east facing slopes in N. hemisphere) TERM 3 Glacial Trough DEFINITION 3 U shaped valley carved by alpine or valley glacier TERM 4 Hanging Valley DEFINITION 4 drop left where minor glacier joined with major glacier TERM 5 Roche Moutonee DEFINITION 5 asymmetricrock knob created by regelation plucking (along flow of glacier) TERM 6 Striations/polishing DEFINITION 6 scrape marks parallel to direction of glacier travel TERM 7 Truncated Spur DEFINITION 7 mountain ridge cut off by glacier passing below TERM 8 Tarn DEFINITION 8 lake left in depression at base of cirque TERM 9 Ground Moraine DEFINITION 9 general term for layer randomly dropped underneath glacier TERM 10 Flutes DEFINITION 10 long, broad grooves scooped out of material over which a glacier has passed TERM 21 Kettle DEFINITION 21 sunken holes in kame terraces or moraines or outwash plain, filled with water TERM 22 Outwash Plain DEFINITION 22 apron of sediment deposited in front of a glacier, result of many braided streams TERM 23 Varve DEFINITION 23 thin, alternating light and dark layers representing annual differences in texture and organic matter TERM 24 Turbidity Currents DEFINITION 24 underwater landslides of material moving from near shore to deeper water TERM 25 Dropstones DEFINITION 25 rocks that are carried by ice into deeper water, then dropped as ice melts TERM 26 Loess DEFINITION 26 silt-sized particles created as rock is ground up by glacier, often occurs in thick, extensive, blanketing layers TERM 27 Sand Dunes DEFINITION 27 coarser particles and generally smaller extent than loess TERM 28 Major Types of Glaciers DEFINITION 28 Cirque Glaciers--flowing ice streams restricted to amphitheater-shaped depressions in valley headlandsValley glaciers--streams of ice that flow downvalley well beyond the cirqueIce Sheets--Broad, flowing ice masses that are not confined to valleys; ice accumulates to massivethicknessin high-latitude continental areas or broad uplands TERM 29 Intermediate Types DEFINITION 29 Mountain ice sheets--valley glaciers that enlarge to form ice sheets that bury all but the highest Alpine peaksPiedmont glaciers--glaciers that discharge ice onto broad lowlands located along the base of mountains TERM 30 Dynamic Classification DEFINITION 30 Active Glaciers--characterized by high rates of ice movement from accumulation zones to their terminusPassive Glaciers-- low rates of ice movement from accumulation zones to ablation zonesDead Glacier--possesses nodiscernibleinternal ice flow TERM 31 Thermal Classification DEFINITION 31 Temperate Glaciers--ice is at or near its pressure melting point throughout ice massPolar GlaciersSubpolar--Ice mass is generally below the pressure melting point except for summer melting of the upper few metersHigh-Polar--ice mass below the pressure-melting point at all times TERM 32 Taliks DEFINITION 32 water pockets in permafrost, often contain high amounts of salts and dissolved chemicals, which decreases the freezing point of the waterProblems these cause: settlement, flooding, heave TERM 33 Periglacial Regions DEFINITION 33 1. Intense frost action2. low precipitation (more snow=thermal blanket)3. seasonally, snow free ground4 underlain at depth by permafrost TERM 34 Frost Heaving DEFINITION 34 vertical movement from freezing of active layer and taliks (9% plus crystal growth) TERM 35 Frost Cracking DEFINITION 35 Fracturing by shrinking of already frozen ground TERM 46 Accumulation DEFINITION 46 at head of glacier new snow-->firn-->ice TERM 47 Ablation DEFINITION 47 loss, mostly at toe of glaciermeltingsublimation--ice to gas due to wind altering humiditywind erosioncalving--big chunks fall off TERM 48 Equilibrium line altitude DEFINITION 48 elevation for particular glacier where net accumulation=net ablation TERM 49 Positive Mass Balance DEFINITION 49 Glacier advances, toe is steep with clean ice (adding more than melting) TERM 50 Negative Mass Balance DEFINITION 50 Glacier retreats, toe gently sloping, dirty ice (melting more than adding) TERM 51 Convex DEFINITION 51 When a glacier travels over a convex surface, the glacier is extended and cracks TERM 52 Concave DEFINITION 52 When a glacier travels over a concave surface, the glacier is compressed*Note--glaciers do not push material backwards! on top or eventual sinking TERM 53 Abrasion DEFINITION 53 Depends on:debris supply (fresh, angular, large is best) and underlying rock hardnessbasal sliding velocityice thickness, shearbasal meltwater (more = less shear) TERM 54 Regelation Plucking DEFINITION 54 the saturation and refreezing of cracks along the surface of a glacier's path that plucks pieces of rocks TERM 55 Meltwater Flow DEFINITION 55 Channels under most warm glaciers, preserved only in rock TERM 56 3 Reasons Glacial Meltwater Streams are effective erosional agents DEFINITION 56 3. Increased Pressure=more energy2.Sediment loads are fresh and angular1. Velocity, steep areas TERM 57 Till DEFINITION 57 material dropped in place above, within, below, or on edges of glacier TERM 58 Glaciofluvial Outwash DEFINITION 58 material carried by running water above, within, below, or in front of glacier TERM 59 Basal lodgement till DEFINITION 59 solid rock TERM 60 Ablation till DEFINITION 60 shovelable, immediate melting TERM 71 Silica Content DEFINITION 71 Silica, usually present in continental volcanoes (continental crust)when more silica is present, more explosive lava (viscous)least to most viscous: basaltic andesitic granitic TERM 72 Gas Content DEFINITION 72 more porous, more explosive TERM 73 Island Arcs DEFINITION 73 basaltic (iron, mg) composition (Japan) TERM 74 Continental Subduction Zones DEFINITION 74 More silicic (andesite to rhyolite), dense ocean crust is buried under continental crust. Melted material rises and gains silicaAndes TERM 75 Hotspots DEFINITION 75 Hawaii--oceanicYellowstone--continentalandesitic to basaltic TERM 76 Spreading Centers DEFINITION 76 Basaltic TERM 77 Flow DEFINITION 77 pahoehoeaascoria/pumice (vesicular gas pockets)destroys more ground TERM 78 Tephra DEFINITION 78 thrownash=powdertuff=solidified ashlapilli 2-64mmbombs >64 mmlargest area covered TERM 79 Gas Flow DEFINITION 79 pyroclastic flow, or ignimbrite (kills most)gas+lava=fastdirected TERM 80 Lahar DEFINITION 80 volcanic debris + water = flow(water from melted ice, snow, or rainwater)directed TERM 81 Cinder Cone DEFINITION 81 small, all tephra, angle of repose TERM 82 Basalt Dome/Shield Volcano DEFINITION 82 Huge, low slopes, deeply eroded TERM 83 Composite/Stratovolcano DEFINITION 83 tephra interbedded with flows---large, high slopes (Mt. St. Helens) TERM 84 Caldera DEFINITION 84 collapse of larger cone into magma chamber TERM 85 Batholith DEFINITION 85 diapir intrusion, usually acidic/granite (pikes peak) large