Soil Texture and Composition: Terms and Definitions, Quizzes of Forestry

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TERM 1 Pedology DEFINITION 1 Study of soil properties, formation and classification TERM 2 Soil Texture DEFINITION 2 Refers to the particle size of the soil material- whether it is fine or coarse, how it feels when you rub it in your handsThere are different sized particles that make up soil Sand: 0.05-2mm (50-2000 micrometers) ="gritty" Silt: 0.002-0.05mm (2-50 micrometers)= "smooth" Clay: <0.002mm (<2 micrometers)= "stiff and waxy" Textural classes of soil are defined mixtures of sand, silt, and clay that can be differentiated by feeling TERM 3 Textural Triangle DEFINITION 3 Plot the percentages of sand, silt, and clay to determine the textural classes of the soil TERM 4 Ribbon Test DEFINITION 4 Testing the feel and length of a ribbon of soil to determine the textural class No ribbon: very gritty= Sand, loamy sand <1" ribbon: v. gritty= sandy loam; neither= loam; v. smooth= silt loam 1-2" ribbon: v. gritty= sandy clay loam; neither= clay loam; v. smooth=silty clay loam >2" ribbon: v. gritty= (sandy) clay; neither= clay; v. smooth= (silty) clay TERM 5 Loamy Textures DEFINITION 5 Form weak (1") ribbon and low in clay Sand Loamy sand Sandy loam Loam Silt loam TERM 6 Sand DEFINITION 6 Loamy texture Non-cohesive: will not form a ball or a ribbon Very gritty TERM 7 Loamy Sand DEFINITION 7 Loamy texture Forms a weak ball but no ribbon Very gritty TERM 8 Sandy Loam DEFINITION 8 Loamy texture Forms a weak (<1") ribbon Very gritty TERM 9 Loam DEFINITION 9 Loamy texture Forms weak (<1") ribbon Intermediate (some) grittiness TERM 10 Silt Loam DEFINITION 10 Loamy texture Form a weak to moderate (1 to 1-1/2") ribbon Very smooth (little grit) TERM 21 Munsell System DEFINITION 21 Describes soil color based on matching soil colors to standardized color chips contained in a booklet (soil must be moist when comparing) Each color chip has a series of properties that form the name of the chip: Hue Value Chroma Example: 10YR 5/4= 10YR hue page, value of 5, and chroma of 4 TERM 22 Hue DEFINITION 22 Property used to help define a soil color (Munsell System) The dominant spectral color of an entire page of chips in the booklet Hue of 10YR indicates all chips on that page have a basic color composed of 10 parts yellow (Y) and 1 part of red (R) TERM 23 Value DEFINITION 23 Property used to help define a soil color (Munsell System) Lightness of darkness of the color, meaning the amount of white or black mixed into the spectral color Values range from 2 at the bottom to 8 at the top of the page High values being a light color (white added) and a low value being a dark color (black added) Low value colors often indicate high humus contents TERM 24 Chroma DEFINITION 24 Property used to help define a soil color (Munsell System) The brightness or dullness of a color chip, ranging from 1 to 8 along the bottom of the page of chips Low chroma number (< 2) indicate dull (grayish) colors with little of the hue mixed in; tend to be reduced (waterlogged) soils High chroma numbers are bright colors; tend to be well- oxidized TERM 25 Matrix and Mottles DEFINITION 25 Some soils have multiple colors present within one horizon Matrix= the main background color Mottles= other colors TERM 26 Soil Structure DEFINITION 26 Refers to organization of primary soil particles (sand, silt, and clay) into secondary units called aggregates (peds)-->occur due to cohesive action of finer silts and clays, also humus of soil Only A,E, and B horizons have peds; C horizon= single-grained or massive Types of structures: 1) Granular, 2) Platy, 3) Blocky, 4) Prismatic/ Columnar Types of Structureless: 1) Single- grained, 2) Massive Structure modified by size and grade descriptors TERM 27 Granular DEFINITION 27 Type of soil structure Rounded, porous, soft Common in A and E horizons Formed by the cohesive action of humus Size: Coarse (>1/2") Fine (<1/16") Medium (in between) TERM 28 Platy DEFINITION 28 Type of soil structure Plate-like A and E horizons; occasionally B or C TERM 29 Blocky DEFINITION 29 Type of soil structure Angular or sub-angular, peds with sharp faces and corners Common in B horizons Size: Coarse (>2") Fine (<1/4") Medium (in between) TERM 30 Prismatic/ Columnar DEFINITION 30 Type of soil structure Elongated vertically Occasional in B horizon TERM 31 Single- Grained DEFINITION 31 Type of Structureless soil Very sandy materials without structural units TERM 32 Massive DEFINITION 32 Type of Structureless soil Cemented or rock-like Found in C horizons TERM 33 Grade of Ped Structures DEFINITION 33 Weak: Peds barely visible; most of soil is unsaturated Strong Distinct peds; most of soil is in structural units Medium In between TERM 34 Consistence DEFINITION 34 Describes the degree of cohesion of peds, or their resistance to crushing (how difficult the peds are to crush) Loose Friable Firm Very firm TERM 35 Loose DEFINITION 35 Type of consistence of peds No peds present (used with single-grain structure) TERM 46 Hydrolysis of Muscovite (Mica) DEFINITION 46 Muscovite + H+ ----> clay minerals + K+ Muscovite (platy mineral) which potassium, K, occurs between thin sheets, holding it together Protons are able to replace the K and cause muscovite to break apart, creating clay minerals (See "Rock" flashcards for Muscovite/ Mica) TERM 47 Clay Minerals DEFINITION 47 Can refer to group of mineral or particle size TERM 48 Where does the acidity (protons) that initially cause Hydrolysis come from? DEFINITION 48 Rainwater contains some acidity (pH= 5.5) in the form of carbonic acid due to the solubility of CO2 gas in water CO2 (g) + H2O ---> H2CO3 (Carbonic Acid) ---> H+ + HCO3- (Bicarbonate) Protons created initiate the weathering cycle TERM 49 Oxidation- Reduction DEFINITION 49 -Type of Chemical weathering-Involves e- transfer causing a change in the valence state of an atom, with iron, Fe, being most important example TERM 50 Oxidation-Reduction of Iron (Fe) and Oxygen (O2) DEFINITION 50 Fe+2 (reduced) ---> Fe+3 + e- (oxidized) -In most primary minerals, Fe= reduced, due to low O2 during form.; -O2 exposed @earth's surface=able to accept e- from Fe & oxidize it O2(g) (e- acceptor) + 4e- + 2H + 2OH- -Biotite & ferro- magn. minerals (high in Fe)= unstable= exposed to O2 -- > Fe+2 oxidizes to Fe+3 & minerals breakdown. Resulting in :-Ferromag. (Fe+2) + O2 --> Ferromag (Fe+3) --> clay minerals + -Fe+3Soluble Fe released hydrolyzes to form solid iron hydroxide Fe+3 + 3H2O ---> Fe(OH)3(s) ("rust")+ 3H+ (source of red yellow pigment) TERM 51 Oxidizing Agent DEFINITION 51 Electron (e-) acceptor TERM 52 Hydration- Dehydration DEFINITION 52 Involve the gain or loss of water, but do not H+ as reactant or productMost important= dehydration of Fe(OH)3 produced by oxidation Fe(OH)3 ("rust") ---> FeOOH (geothite:yellow) + H2O (WET) 2FeOOH ---> Fe2O3 (hematite: red) + H2O (DRY) TERM 53 Solution DEFINITION 53 Dissolution of minerals in water to form soluble ionsSoluble minerals Halite Gypsum Insoluble Minerals Quartz Calcite= limestone (See "Rocks" flashcards) TERM 54 Soluble Minerals DEFINITION 54 Minerals that dissolve rapidly and leach thru the soil:NaCl (halite) -- > Na+ + Cl- (very soluble)CaSO4 (gypsum) --> Ca+2 + SO4-2 (pretty soluble) In B horizon of desert- where rainfall is limited CaCO3 (calcite) + H2CO3 (carbonic acid) --> Ca+2 + 2HCO3- (bicarbonate) Calcite= major mineral in limestone; rxn sometimes called carbonation (see "Rocks" flashcards) TERM 55 Insoluble Minerals DEFINITION 55 Minerals that are resistant to weathering in soil:SiO2 (quartz) + 2H2O -->H4SiO4 (aq) (silicic acid) Slowly depletes quartz from soils over geologic time- older soils are lower in SiO2 (See "Rocks" flashcards) TERM 56 Weathering of Primary Minerals DEFINITION 56 Soluble (50 yrs): Halite, Gypsum; Product= ionsEasily weathered (100 yrs): Calcite; Product= none & Biotite; Product=Clay, Fe OxidesSlowly weathered (1000 yrs): Feldspar; Product= Clay & Ferromag.; Product= Clay, Fe OxidesV. slowly weathered (10^6 yrs):Muscovite; Product=Clay & Quartz; Product= noneStable: Clay Minerals; Products= none & Fe Oxides; Products= none TERM 57 Results of Weathering DEFINITION 57 Particle size is reduced and porosity increased; the surface area of particles is also increased Net impact of these physical changes= water is now able to penetrate into the rock mass and react chemically with the exposed inner surfaces of the rock Chemical changes include loss of soluble and easily weathered minerals, and the formation of new secondary minerals within the weathered rock TERM 58 LeChantlier's Principle DEFINITION 58 Equilibrium between reactants and products If more reactants, reaction pushed to left (make more products) If more products, reaction pushed to right (make more reactants) TERM 59 What makes the oceans salty? DEFINITION 59 All weathered products and soluble salts are washed into the ocean TERM 60 Residual Parent Material DEFINITION 60 Parent Material that forms in place from the weathering of rock, without movement within the landscape Found on upland areas Felsic vs. Mafic (intermediate=schists, diorites) Clastic sedimentary and meta-sedimentary rock Calcitic rocks