SCSC 301 Exam 1
the parent material transported by wind is _______ a. residuum b. glacial till c. colluvium d. alluvium e. eolian
e. eolian
what is a drumlin?
elongated whale shaped hill formed by glaciers acting on other glacial till or moraine
What is a polypedon?
group of similar pedons
what is weathering by chemical processes?
hydration, hydrolysis, redox, dissolution, acid dissolution, complexation
what is hydration?
intact water molecules changing the structure of minerals
What is it called when there is a dominant influence of this one particular soil forming factor: parent material?
lithosequence
what is redox (oxidation/reduction)?
minerals with iron, manganese, and sulfur are susceptible to redox reactions which describe the crystal structure and cause it to break down. -redox reaction: a chem reaction where the oxidation state of an element is chaaged by an electron transfer -oxidation: atom loses an electron -reduction: atom gains an electron
What is biological weathering?
plants and microbes do both physical and chemical weathering processes
Describe the C horizon:
regolith
Describe the R horizon
rock
What is a pedon?
smallest 3D unit of soil with all the soil characteristics
What is it called when there is a dominant influence of this one particular soil forming factor: topography?
toposequence
What type of transportation gives medium to high sorting?
transportation by water or wind
what is hydrolysis?
water molecules split into hydroxyl and hydrogen ions at the mineral surface and part is absorbed into the mineral , the hydrogen ion often replaces the cation
what is dissolution?
when minerals dissolve in water
A soil sample occupies 30 cm3 and weighs 50 g when wet. When dry, the soil occupies 20 cm3 and weighs 42 g. What is the gravimetric water content of this soil sample?
(mass water)/(dry mass soil) .19
Name minerals and solubility: oxides
-Fe and Al oxides-not soluble and last products of weathering -hematite, goethite, and gibbsite
What is the classification of parent material that was transported by flowing water?
-alluvial -degree of sorting: med-high -coarse fragments?: in high energy environments -flowing water carries sediments that are deposited in 3 general classes 1. floodplain 2. alluvial plan 3. delta
Plant Essential Elements
-carbon -boron -hydrogen -oxygen -phosphorus -potassium -nitrogen -sulfur -calcium -iron -chlorine -manganese -molybdenum -nickel -copper -zinc -magnesium
What are the 5 soil forming factors?
-climate (active) -biota (active) -parent material (passive) -topography (modifying) -time (passive)
What is the classification of parent material that was transported by gravity?
-colluvial -degree of sorting: low -coarse fragments?: possible -sediment that has moved downhill by gravity -made of poorly sorted rocks and sediment -example: avalanche -cliff rock debris = detritus
what are sedimentary rocks?
-deposition and recrystallization of weathering products from other rocks -compacted or cemented weathered products EXAMPLES -granite and basalt (igneous) > quartz and feldspar > quartz and sand and clay > sandstone -ca-rich basalt (igneous) > calcite > limestone
what is particle density?
-dry mass/particle (only) volume -2.65 g/cm^3 (mineral particles)
what is bulk density?
-dry mass/total (ie bulk) volume -ranges from 1-2, <1.6 g/cm^3 is best for plants -clay vs sand which has the lower bulk density? CLAY (high micropore space; sand has big but few pores) -AFS (acre furrow slice) has a 1.5 g/cm^3 bulk density and is about 2,000,000 pounds -HFS (hectare furrow slice) has a 1.5 g/cm^3 bulk density and is about 2,250,000 pounds (acre furrow slice is top 6 inches of a soil and hectare furrow slice is top 15 cm of soil i think)
What is the classification of parent material that was transported by wind?
-eolian -degree of sorting: high -coarse fragments?: none -wind picks up material and deposits it elsewhere -types of material largest to smallest: loess (silt often from barren till left from glaciers), aerosolic dust (very small particles, travel over long distances), volcanic ash
What is the classification of parent material that was transported by glacier (ice)?
-glacial -degree of sorting: low -coarse fragments?: possible, random distribution -ice age: as glaciers advanced they gouged the earth and accumulated soil and rock -glaciated valleys are very smooth
What are rocks?
-groups of minerals that form from earth processes -igneous, sedimentary, and metamorphic
Describe the O horizon and state it's other name:
-horizon of partially/wholly decayed OM that may occur over or in place of A horizon -organic horizon
what are metamorphic rocks?
-igenous or sedimentary rocks transformed by high heat and pressure EXAMPLES -granite (ign) > gneiss or shist -quartz (ign) > quartzite -sandtsone (sed) > quartzite -shale (sed) > slate -limestone (sed) > marble
Describe the B horizon and state it's other name:
-subsoil horizon that is the zone of accumulation. usually gain of clay, oxides, salts, and minerals. -accumulation horizon
What does weathering over time result in?
-increasingly smaller particles -increasingly more stable minerals (ie less stable minerals weather away) -release of soluble components (ie loss of elements from the less stable minerals) (Ca^2+, Mg^2+, K^+, Na^+, SO4^2-) -decreases in most primary minerals and increases in secondary minerals -usually accumulation of Fe and Al oxides (most stable minerals ; they are secondary) (this means that soil is typically higher in Fe/Al oxides and lower in basic cations than the parent material)
What is the classification of parent material that was transported by lake?
-lacustrine -degree of sorting: high -coarse fragments?: none -similar to marine PM, except water is from lakes rather than oceans -sediments are often rich in clay and silts -often have layered appearance due to annual deposition of sediments -usually uplifted lakebed
What is the classification of parent material that was transported by ocean?
-marine -degree of sorting: high -coarse fragments?: none -beach or shore deposits -often uplifted sediments -ex: coastal plain soil -horizontal layering -vary from sandey to clayey
what is glacial till?
-materials deposited in place by ice -varies in size from boulders to clay -may appear similar to colluvial material, but usually more rounded
What are the 5 major soil functions?
-medium for plant growth -support for buildings and roads (engineering medium) -habitat for organisms -purification of waters and regulator of water supplies -recycling system for nutrients and organic wastes
What is the classification of parent material that was transported by organic residues?
-organic -usually develop in wet (often cool) areas where plant growth exceeds rate of residue decomposition -excessive wetness inhibits OM decomposition (microbes don't have enough oxygen for aerobic activities that facilitate OM decomposition)
what is complexation?
-organic acids complex or chelate (compound with organic bonded to central metal atom at 2 or more points) many metal cations and remove them from the mineral -the acids are often from plants or decaying OM
Name minerals: silicates
-primary: quartz and SiO2 (dominate in sands and are resistant to degredation), feldspars, amphiboles, pyroxenes, hornblend, mica (these all can form clays) -secondary: kaolinite, smectite, vermiculite, chlorite
Name minerals and solubility: sulfates
-relatively soluble -gypsum
What is the classification of parent material that formed in place?
-residual/residuum -degree of sorting: low -coarse fragments?: possible -develops in place from the underlying rock -warm and humid climates: soils are often leached and oxidized and often red and yellow from oxidized Fe -cool and drier climates: soils are colored similar to rocks they formed from
what are igenous rocks?
-rocks formed from when molten lava cools -felsic (more Na and K and lower melting temp), intermediate, mafic, ultramafic (more iron, magnesium, and calcium and higher melting temp) -minerals with high Fe and Mn are more easily weathered and a darker color -extrusive: formed on surface from lava (fine grained) -intrusive: (coarse grained) formed from magma that cools and solidifies in the crust
Name minerals and solubility: carbonates
-somewhat soluble -calcite and dolomite
Describe the E horizon and state it's other name:
-subsoil horizon that is zone of elevation (depletion) that usually has lots of clay, oxides, salts, minerals, and OM. Usually light colored -depletion horizon
Describe the A horizon and state it's other name:
-the topmost mineral horizon -top mineral horizon
What are the differences between topsoil and subsoil?
-topsoil (horizon A): more affected by soil forming factors (darker, more organisms) & usually more porous, smaller aggregates, less clay and more sand/silt -subsoil (horizon B): less affected by soil forming factors (lighter in color, fewer organisms) & usually less porous (more compacted), larger aggregates, more clay
Name minerals and solubility: phosphates
-very insoluble -apatite
Name minerals and solubility: halides
-very soluble -halite, sylvite
The range in bulk density for typical mineral soils that are suitable for plant growth is ________g/cm3
1.2 to 1.6
What is the mass of 1 ha of soil to 15 cm depth (1 ha = 10,000 m2, density of water = 1000 kg/m3 = 1 g/cm3, soil bulk density = 1.5 Mg/m3
2,250,000 kg M=(bulk density)*(Volume) V=(area)*(depth) V=(10,000)*(15cm>>>.15m) M=(1.5Mg/m^3>>>>1500kg/m^3)*V
Which value most likely represents the particle density of a soil?
2.6
What three elements are common elements but NOT ESSENTIAL for plants?
Al (aluminum), Si (silicon), and Na (sodium)
What factors affect aggregation?
CATION TYPE -Ca improves aggregation, Na does not NATURAL CAUSES OF SOIL MOVEMENT -wetting/drying -freezing/thawing -expanding (heat)/contracting (cool) ORGANISMS -plants, microbes, animals -humans SUBSTANCES THAT CEMENT OR STABILIZE AGGREGATES -microbial gums -iron oxides -carbon -clay
what is the density formula?
DRY mass/volume
The most probable sequence of aggregate types from the surface downward in a soil is:
Granular, subangularblock, massive
The transformation of a primary mineral to a secondary mineral could occur through which process?
Hydrolysis
Aggregation helps fine‐textured soils become more suitable for plant growth because it ________
Increases macroporosity
From a plant's perspective, the most important role of soil structure in fine‐textured soils is to increase____.
Macroporosity
The structure of a soil horizon is reported as "strong, medium, crumb". Which is the structural size?
Medium
Surface soils are ____ than subsoils
More porous
Do soils need to have all the horizons?
No, you really only need C&A or C&O, all others are additional
What horizons are part of the soil solum?
O, A, E, B (everything above horizon C/everything affected by soil forming factors)
What are the 5 soil horizons?
O, A, E, B, C
Aggregation of soil particles is related to the content of
Organic matter and clay
Bulk density is the oven dry mass of soil divided by ________________
Particle plus the pore volume
Reactivity of materials in soils is primarily a function of ____________
Particle size
A major assumption made in applying Stoke'sLaw to sedimentation of soil particles in a cylinder is
Particles will settle in order of decreasing size and density (i.e., large dense particles settle first
What is regolith and why horizon represents it?
Regolith is the deepest layer of soil/parent material that is unaffected by soil forming factors
What are the primary particles of soil and describe them?
SAND -largest -low affinity for water, nutrients, and each other SILT -medium sized -moderate affinity for water, nutrients and each other -low affinity for nutrients CLAY -smallest (largest surface area) -high affinity for water, nutrients, and each other -tends to aggregate -can act as a colloid
What are the four major soil components and their percentage?
SOLIDS -mineral matter (45%) -Organic matter (5%) PORE SPACE -air (25%) -water (25%)
Particle sizes arranged in order from least to most adsorptive are _____
Sand, silt, clay
The most probable sequence of soil textures surface to subsoil (e.g., A, B1, B2) is
Sandy loam, clay loam, clay
Soil compaction has no effect on _________
Soil texture
Which physical soil property is an inherent property of the soil that cannot be changed in our lifetime?
Soil texture
what is marl?
a soft, calcite-rich material that is often deposited with clays in a marine environment
which of the following contains only plant essential elements that are common in rocks and soils? a. Ca, Mg, K, Fe b. Ca, Mg, Si, Na c. Ca, Mg, Na, Fe d. Ca, Al, Si, Fe e. Si, Al, Ca, K
a. Ca, Mg, K, Fe
primary minerals that may weather to form secondary clay minerals in soil include: a. feldspars, hornblende, and mica b. feldspars, quartz, and calcite c. apatite, hornblende, and gypsum d. apatite, feldspars, and calcite e. feldspars, hematite, and goethite
a. feldspars, hornblende, and mica
given the scenarios below, which is most likely: a. surface soils are more porous, less dense, and typically of coarser texture than subsoils b. surface soils are more porous, denser, and typically coarser texture than subsoils c. surface soils are less porous, denser and typically of coarser texture than subsoils d. surface soils are less porous, less dense and typically of finer texture than subsoils e. surface soils are more porous, denser and typically of finer texture than subsoils
a. surface soils are more porous, less dense, and typically of coarser texture than subsoils
what is weathering by physical processes?
abrasion by wind, water, ice, gravity
what is a moraine?
any glacially formed accumulation of unconsolidated glacial debris (soil and rock, ie glacial till) -adjacent to a moraine, there is usually an outwash plan that is made of glacial outwash (where materials are pushed out)
a soil typically contains a higher percentage of ______ than the rock from which it is derived a. Ca b. Al c. P d. Si e. K
b. Al
soil is a dynamic natural body having properties due to the combined effects of __________ as modified by topography acting on parent material over time a. weather and temperature b. climate and biota c. slope and time d. climate and rainfall e. organisms and parent material
b. climate and biota
which of the following parent materials has a very low degree of sorted materials? a. loess b. glacial till c. alluvial fan d. delta e. volcanic ash
b. glacial till
which of the following mineral is the most soluble? this high solubility causes it to be easily weathered and be lost from soil profiles a. hematite b. gypsum c. hornblende d. quartz e. gibbsite
b. gypsum
the chemical composition of minerals in a residual soil usually has a ______ from that of a parent rock a. lower percentage of Fe and Al b. lower percentage of basic cations (ie Ca, Na, Mg, and K) c. higher percentage of basic cations (ie Ca, Na, Mg, and K) d. higher percentage of granite e. none of the above
b. lower percentage of basic cations (ie Ca, Na, Mg, and K)
alluvium is parent material that is transported by ________ a. wind b. water c. ice d. gravity e. organic matter
b. water
What is weathering?
biological, chemical, and physical processes that destroy or decompose rock to eventually form soil particles
What is it called when there is a dominant influence of this one particular soil forming factor: biota?
biosequence
which size aggregates are better, big or small?
both are needed, want a mix, typically larger particles are more fragile and are easily lost via management
a typical moist surface soil ideally contains _________ % water on a volume basis a. 5 b. 10 c. 25 d. 45 e. 50
c. 25
which horizons in a soil containing A, B, C, and R horizons are included in its soil solum? a. A, B, C, R b. A, B, C c. A, B d. O, A, B e. O, A, E, B
c. A, B
a soil that supports plant life must provide all of the following, EXCEPT a. nutrients b. oxygen c. carbon dioxide d. water e. physical support
c. carbon dioxide
a two-dimensional vertical cross-sectional view of a soil is referred to as a soil _______ a. solum b. pedon c. profile d. horizon e. regolith
c. profile
What is it called when there is a dominant influence of this one particular soil forming factor: time?
chronosequence
What is it called when there is a dominant influence of this one particular soil forming factor: climate?
climosequence
what is glacial outwash?
coarse grained alluvium, mostly gravel and sand, flowing from melt water
intensive weathering typically results in soils with high concentration of __________ because these are secondary minerals that are resistant to further weathering a. calcite, dolomite, and gypsum b. hornblende and feldspar c. granite and basalt d. hematite and gibbsite e. hornblende and marble
d. hematite and gibbsite
which of the following weathers to form silicate clay minerals in soils? a. hematite b. quartz c. calcite d. hornblende and feldspar e. limestone
d. hornblende and feldspar
which of the following soil forming factors is passive? a. biota b. weathering c. climate d. parent material e. leaching
d. parent material
a primary silicate mineral that is resistant to weathering is: a. hematite b. apatite c. mica d. quartz e. dolomite
d. quartz
what is acid dissolution?
when weathering is accelerated by acid and acid enhances dissolution and hydration reactions. Acid comes from many sources like water, root and microbe respiration (CO2 > carbonic acid), organic acids from roots, decomposition of organic materials, and mineral acids from mineral decomposition (pyrite > sulfuric acid)