ESS midterm 1
If the total water potential in the soil around a plant root were -50 kPa, water would move from the soil into the root if the water potential inside the root cells were ___ kPa. anything between +50 and -50 -5 +100 +5 -100
-100
write the terrestrial water balance equation. Make sure to (1) spell out the terms and (2) write the equation in the same exact way and order as in the lecture/textbook.
P = ET + SS + D Precipitation = Evapotranspiration + Soil Storage + Discharge (runoff)
A valley with shallow soils overlaying impermeable bedrock is drained by a single river. It receives 680 mm of precipitation per year, approximately half as snow and half as rain. From measurements of the river's depth, width, and velocity, it is determined that approximately 450 mm of water is discharged each year. How much water [mm] is lost from the valley to the atmosphere by evapotranspiration?
P = ET + SS + D (water balance equation) 230 mm
Explain the Land Energy budget Equation
R_net = G + H + λE R_net = Vis + LR = Net Radiation, Incoming and leaving from the sun G = Ground heat flux ( H = Sensible heat flux (heat we feel, from surface and atmoshpere) λE = Latent Heat (Heat from water) (Evapotranspiration)
The texture class of a soil that consists of 50% sand and 10% silt is ________. Refer to the texture triangle Silty clay loam Loam Clay Sandy clay Sandy loam
Sandy clay
Clay soils have smaller pores and hold considerably less water than sandy soils. (True/False)
False
Poorly drained soils or soils saturated by water tend to be yellowish-brown or reddish. (True/False)
False
The process of aerobic respiration is a significant source of which of the following gases? methane oxygen hydrogen sulfide carbon dioxide nitrogen ammonia
carbon dioxide
What is the CEC of a soil that contains the following amounts of various exchangeable ions (units are cmolc/kg): 2 of H+, 3 of Al3+, 5 of Ca2+, 1 of K+, 3 of Mg2+, 0.5 of Na+, 1 of NH4+, 3 of SO4-2, and 1 of NO3-. 15.5 10.5 19.5 11.5 19.0
15.5 Therefore, H+,Al3+,Ca2+,K+,Mg2+,Na+ and NH4+ are cations 2+3+5+1+3+0.5+1 Reminder: CEC = Cation exchange capacity. The number of moles of positive charge cmolc/kg stands for "centimols of charge per kilogram soil"
About how long does it take for parent rock to be converted into good soil? 1-10 years 20-200 years 1000-2000 years 2000-20,000 years 50,000-100,000 years
2000-20,000 years
Which of the following statements is TRUE? 2:1 silicate clay consists of one octahedral sheet sandwiched between two tetrahedral sheets. Kaolinite is the most prevalent colloid in soils developed form volcanic ash (Andisols). The order of strength of adsorption of ions by most colloids when they are present in equivalent quantities is Al>Ca>K>Mg>Na. Soil colloids can be differentiated by their shapes using ordinary light microscopes. Vermiculate clays have a net electropositive charge in slight acid soils.
2:1 silicate clay consists of one octahedral sheet sandwiched between two tetrahedral sheets. Why the others are wrong: Kalolinite is a crystalline soil colloid. While volcanic ash is a noncrystalline soil colloid The order of strength follows H+ > Al > Ca > Mg > K > Na Soil colloids are 1-2 micrometers which cannot be observed in an ordinary light microscope Lecture 8 slide 35: Vermiculate clays are 5% pH dependant. Therefore they do not have a change in slight acid soils. SO small it's negligible
You collect a soil sample in the field. It weighs 150 g and has a bulk density of 1.3 Mg/m3. You dry it for a week and weigh it again. It now weighs 105 g. What was the gravimetric water content of this sample? 45% 43% 70% 30% 56%
43%
Mechanical weathering would predominate. A cold, wet environment at high elevation, in which freezing and thawing is common. A cold, dry environment experiencing uplift, in which material is being removed by erosion from an underlying pluton/intrusive igneous rock. A warm, wet environment with above average yearly rainfall and several stormy seasons each year. A hot, humid climate with heavy precipitation that occurs all year. A hot environment with many short but intense rainstorms.
A cold, wet environment at high elevation, in which freezing and thawing is common. A cold, dry environment experiencing uplift, in which material is being removed by erosion from an underlying pluton/intrusive igneous rock. Chemical weathering is tends to be more predominant in warmer weather, because increased temperature speeds up chemical reactions and wet conditions where there is enough water to help produce acidic substances, and where living organisms that produce rock breaking acids can thrive. Hence, cold and wet conditions favor mechanical weathering and hot and wet favors chemical weathering.
Chemical weathering would predominate. A cold, wet environment at high elevation, in which freezing and thawing is common. A cold, dry environment experiencing uplift, in which material is being removed by erosion from an underlying pluton/intrusive igneous rock. A warm, wet environment with above average yearly rainfall and several stormy seasons each year. A hot, humid climate with heavy precipitation that occurs all year. A hot environment with many short but intense rainstorms.
A warm, wet environment with above average yearly rainfall and several stormy seasons each year. A hot, humid climate with heavy precipitation that occurs all year. A hot environment with many short but intense rainstorms. Chemical weathering is tends to be more predominant in warmer weather, because increased temperature speeds up chemical reactions and wet conditions where there is enough water to help produce acidic substances, and where living organisms that produce rock breaking acids can thrive. Hence, cold and wet conditions favor mechanical weathering and hot and wet favors chemical weathering.
Which cation would you expect to be most tightly held in soil at pH 4.5? Al3+ Mg2+ K+ Na+ Ca2+
Al3+ recall: lecture 9 slide 29 The smaller the cation size and the greater the electronegativity the more "tightly held the cation. Therefore, at soild pH 4.5, an acidic solution. It will highly favor the traits listed above. Al3+ > Sr 2+ > Ca2+ > Mg2+ > Cs+ > K+ > = NH4+ > Na+ . Li+
The soil horizon in which leached mineral particles such as clay and salts tend to accumulate is the. A horizon. B horizon. C horizon. O horizon.
B horizon
An E horizon is more likely to develop in grassland soils than in forest soils. (True/False)
False
What do freeze-thaw and salt weathering have in common? Both freeze-thaw and salt weathering require rain and force rocks apart physically. Both freeze-thaw and salt weathering force rocks apart physically. Only salt weathering requires rain. Both freeze-thaw and salt weathering require rain. Only salt weathering forces rocks apart physically. Both freeze-thaw and salt weathering force rocks apart physically. Only freeze-thaw weathering requires rain. Both freeze-thaw and salt weathering require rain. Only free-thaw weathering forces rocks apart physically.
Both freeze-thaw and salt weathering require rain and force rocks apart physically.
The processes of chemical weathering results in the decomposition of minerals within rocks over time. Fill in the sentences below to explore the different chemical weathering processes. _________ weathering alters the internal structure of rock materials. Potassium feldspar weathers in the presence of water containing ____________. Iron weathers through the process of __________. A greenhouse gas called ____________ influences the rate of chemical weathering.
Chemical weathering alters the internal structure of rock materials. Potassium feldspar weathers in the presence of water containing carbonic acid. Iron weathers through the process of oxidation. A greenhouse gas called carbon dioxide influences the rate of chemical weathering.
Organic matter has a much higher CEC at pH 5.5 than at pH 8.0. (true/false)
False Reminder: CEC is the Cation exchange capacity, the number of moles of positive charge it can absorb Lec 9 slide 32 And organic matter as a Colloid is VERY pH dependant . Lecture 8 slide 35. Therefore, As you decrease the pH (more acidic). The number of protons in solution increases which can protonate oxygen on the organic O groups. However, we need it to be a basic solution in order to DEprotonate the OH organic groups which will then attract and absorb positive charge.
Soils in humid, tropical regions under rain forest are most closely associated with which type of colloid? Allophane Fe, Al oxides Vermiculite Smectite Illite
Fe, Al oxides Lecture 8 slide 25
With the addition of water, the minerals in granite rocks chemically weather into other minerals, known as products. Test your knowledge of the by-product of each mineral as a result of chemical weathering by labeling the minerals below with their respective products. Feldspar Quartz Olivine Products: No chemical change Limonite Clay
Feldspar -> Clay Quartz -> No chemical change Olivine -> Limonite The minerals in granite rocks chemically weather into other minerals, known as products. Just as these minerals within granite, an intrusive igneous rock, crystallized from magma at different temperatures, they also have different resistance to chemical weathering. Minerals like quartz, which crystallize at low temperature are less susceptible to chemical weathering than minerals like feldspar, which crystallize at high temperatures
Evaporation and transpiration are limited by the availability of water and [other].
From the Water balance equation P = ET + SS + D ET = Evaporation & Transpiration = Evapotranspiration They are both limited by energy from the sun. The more energy the more transpiration and evaporation can occur.
Three types of chemical weathering processes are particularly important for transforming minerals within rocks into weathered products. These are hydrolysis, oxidation, and dissolution. Through hydrolysis reactions, minerals are weathered in the presence of water, often rainwater. Through oxidation reactions, iron-rich materials transform in the presence of oxygen in air. And through dissolution, minerals dissolve in water, making their chemical products ions within water. You will sort each example into its category of chemical weathering process. Feldspar in granite rocks weathering to clay. Red color of rocks in Arches National Park. Yellow-stained rocks that used to contain pyrite before it is weathered. Caves formed in limestone. The salty taste of ocean water.
Hydrolosis: Feldspar in granite rocks weathering to clay. Oxidation: Red color of rocks in Arches National Park. Yellow-stained rocks that used to contain pyrite before it is weathered. Dissolution: Caves formed in limestone. The salty taste of ocean water.
The reaction 2KAISi3O8 + 2H+ + 9H20 → H4Al2Si2O9 + 4H4SiO4 + 2K is an example of Hydrolysis Hydration Abrasion Reduction Oxidation Dissolution
Hydrolysis
Which of these is NOT an ecosystem service provided by soils. A lot of different organisms live in soils. Therefore, soils contribute to the biodiversity of a region. Water percolating through soils is purified as contaminants are retained on mineral surfaces and/or degraded by microorganisms. Soils can mitigate flood risk. Soils can take up water, store it, and release it slowly into rivers and groundwater aquifers. Large amounts of the greenhouse gases carbon dioxide and methane are locked up in soils. Soils can be used to grow food and feed. Soils have the capacity to sequester large amounts of carbon in the form of soil organic matter.
Large amounts of the greenhouse gases carbon dioxide and methane are locked up in soils.
Isomorphous substitution creates net negative charges in clay micelles. A typical example of this process is the substitution of __________. two tetrahedral sheets for every octahedral sheet an inner sphere complex for an outer sphere complex two Na+ ions for one Ca2+ ion in a tetrahedral sheet Mg2+ for Al3+ in an octahedral sheet one O2- for one OH- in a tetrahedral sheet
Mg2+ for Al3+ in an octahedral sheet Recall: Lecture 8 Slide 16. Isomorphic substitution, Can happen in both the tetra hedral and octahedral sheet. However, one O2- for one OH- is no change in overall charge. While Mg2+ for Al3+ has an overall decrease in charge. 3+ --> 2+
When a fire occurs in a prairie, it burns very quickly through the grasses. The soil layer most directly affected in this type of fire will be the __________ horizon. A C O B E
O horizon
A smooth feel and matte surfaces indicate a high percentage of which soil separate? sand clay salt Organic matter Silt
Silt Recall: Sand is the largest pore/grain size (very gritty) Clay is the smallest (neither grittiness nor smoothness predominates) and Silt is the second smallest ( which is why it feels smooth) loam is about equal proportions of sand clay and silt
Granite and basalt are both igneous rocks, with different chemical composition and structure, and hence different weathering rates. Minerals that crystallize slowly, like in the case of granite are usually more resistant to chemical weathering than those with a lower crystallization, like basalt. Besides chemical composition, a secondary factor that affects the rate of weathering in such rocks is the amount of cracks/fractures present in a rock will also affect the rate of weathering. Rank the rocks in order of the rate of chemical weathering they would experience, assuming they are all located Slowest Chemical Weathering -> Fastest Chemical Weathering Basalt, with abundant vesicles (holes) Granite, with abundant cracks Basalt, with very few to no cracks Granite, with very little to no cracks
Slowest Chemical Weathering -> Fastest Chemical Weathering Granite, with very little to no cracks (slowest)->Granite, with abundant cracks->Basalt, with very few to no cracks->Basalt, with abundant vesicles (holes) (fastest)
Soils rich in which type of clay would provide the most troublesome site on which to build a road? smectite kaolinite allophane or imogolite chlorite Fe or Al oxides
Smectite Recall: Smectite is a 2:1 expanding crystalline type. Kaolinite is a 1:1 nonexpanding crystalline type Allophane or imogolite is a non crystalline type Chlorite is a nonexpanding 2:1 crystalline type Fe or Al oxides is the last and most weathered type typically found in rain forests
If you were attempting to construct a waste-holding pond on sandy soil, you would haul in clayey soil to line the pond bottom to prevent it from leaking. The best kind of clay to use for this purpose would be _________. illiteallo phane gibbsite smectite kaolinite
Smectite. The most prominent expanding 2:1 Phyllosilicate. Can hold the greatest amount of water. Lec 8 Slide 17
Which of the following statements is incorrect? Soil develops very rapidly, within several years. Plants move nutrients from deep in the soil to the surface. Topography affects the erosion of parent material. Plant roots stabilize the soil surface.
Soil develops very rapidly, within several years.
Which definition correctly describes the term field capacity? The maximum rate at which water can enter a soil. The percentage of water remaining in a soil 2-3 days after it was saturated and free drainage has ceased. The percentage of water in a soil in which all pores are filled with water. The moisture content of a soil at which plants wilt and fail to recover their turgidity when placed in a dark, humid atmosphere. The maximum rate at which water moves through a soil that is satured with water.
The percentage of water remaining in a soil 2-3 days after it was saturated and free drainage has ceased.
Why does water frozen in the cracks of a rock help to break down the rock? Water contracts when frozen and physically forces the rock apart. Water contracts when frozen and chemically forces the rock apart. Water expands when frozen and physically forces the rock apart. Water expands when frozen and chemically forces the rock apart.
Water expands when frozen and physically forces the rock apart.
In soils, water vapor will move from colder to warmer zones. away from fertilizer toward unfertilized regions. from drier areas to moister areas. from areas of warmer to cooler soil.
from areas of warmer to cooler soil.
Eluviation refers to the leaching of minerals and finer soil particles from the upper layers to the lower layers of soil. (True/False)
True
Microorganisms contribute to the formation of soils. (True/False)
True
The greater the depth of water percolation, the greater the depth of weathering and soil development. (True/False)
True
You would expect the cation capacity of Ultisols to be lower those of Aridisols if the soil textures are about the same. (true/false)
True Lecture 8 Slide 36 Lecture 9 Slide 17 Reminder: Ultisols and Adrisols are soil types. They each have different soil colloids in them (a portion of organic or inorganic material that is suspended that carries a charge. Not dissolved in solution as an ion) A major Soil colloid type is a Phyllosilicate, a layered silicate) See Lecture 8 slide 9. Phyllosilicates can be layered in many different ways, Tetrahedral plates sandwiching an octahedral, etc. However, (see Lecture 8 slide 36) a Smectite a 2:1 silicate is more electronegative than a Kaolinite a 1:1 silicate. And by viewing Lecture 9 Slide 17, We can see Ultisols contain less 2:1 silicates (more electro negative Phyllosilicates) while Aridisols contain more 2:1 Silicates
Which of the listed sets of soil properties would result in the warmest soil temperature (at 5 cm depth) on a sunny day in early spring in New York state? The albedo is a measure of how reflective surfaces are for sunlight. Snow-covered surfaces have a high albedo. albedo = 0.35, water content = 0.30, NE aspect, grass-covered soil surface albedo = 0.35, water content = 0.20, SW aspect, bare soil surface albedo = 0.15, water content = 0.15, SW aspect, bare soil surface albedo = 0.15, water content = 0.20, NE aspect, bare soil surface albedo = 0.15, water content = 0.30, SW aspect, grass-covered soil surface
albedo = 0.15, water content = 0.15, SW aspect, bare soil surface
In temperate regions, a surface mulch, such as from leaf litter in a forest or crop residues in no-till farming, will cause the soil to be ______ than it would be if bare (unmulched). warmer in late fall cooler in early spring wetter most of the time all of the above none of the above
all of the above
Productive soils are being degraded or lost by. irrigation that can result in the built-up of salt that is toxic to plants. overgrazing and deforestation that can lead to erosion and desertification of a region. pollution (plastics, heavy metals, pesticides) from poor waste disposal practices, mining, and agriculture. urbanization all of the above
all of the above
Which of the following is (are) an ecosystem service provided by wetlands? storage and filtration of water storage of carbon stabilization of regional climate recreational value all of the above
all of the above
Under unsaturated conditions, water in soil ... moves primarily in larger pores. is not available for plant uptake. can become stagnant when the soil texture abruptly changes from coarse to fine. can become stagnant when the soil texture abruptly changes from fine to coarse. will always move primarily downward.
can become stagnant when the soil texture abruptly changes from fine to coarse.
An important source of acidity in soils that contributes to chemical weathering in soils with circum-neutral pH is carbonic acid, formed from the interaction of soil water and carbon dioxide produced by the respiration of plant roots and soil microorganisms. nitric acid, produced by the respiration of soil bacteria. capsaicin acid, produced by plant roots fending off pathogens. hydrochloric acid, produced during the dissolution of minerals in water. silicic acid, produced during the oxidation of silicate minerals.
carbonic acid, formed from the interaction of soil water and carbon dioxide produced by the respiration of plant roots and soil microorganisms.
Using a textural triangle chart, it can be determined that a soil with 70% clay and 20% silt belongs to the ________ textural class. silty clay loam silt loam clay sandy clay loamy sand
clay Recall: Clay = smallest pore size Silt = second smallest pore Sand = largest pore size
The bulk of soil-air gas exchange takes place by which process? mass flow combustion respiration diffusion dissolution in water cryoturbation
diffusion
Which of the following actions would significantly increase ventilation? increasing the soil's temperature adding organic matter (mulch or manure) to the soil draining the soil of excess water covering the soil in plastic growing a greater number of plants in the soil
draining the soil of excess water
Soils developing from sand and silt carried by the wind are referred to as colluvium fluvial eolian till
eolian
Which of the listed soil colloids has a reasonably high K-level, a CEC of about 20 cmolc/kg, and low tendency to swell when wetted? fine-grained mica kaolinite vermiculite hematite gibbsite
fine-grained mica (non expanding 2:1 Phyllosilicate) Recall: CEC is Cation exchange capacity. The ability of cations to exchange with other higher priority cations. A low tendency to swell when wetted is a non-expanding clay. Therefore the major types are Mica and Chlorites: Lecture 8 slide 21 Remember: Kaolinite is the only 1:1 Crystalline colloid. Which has a low swell capacity. However, CEC is the number of moles of positive charge absorbed per time. Kaolnite is not the most electronegative soil colloid. Lec 8 Slide 37. A range of -1 to -15. This is due to it lacking a gap and less surface area to have negative charge points. While mica has a higher CEC
Which of the following is (are) necessary features for an area to be delineated as a wetland? organic soils shallow standing water aquatic vegetation hydric soils high soil pH
hydric soils
The electronegative charge on 2:1 silicate clays is due primarily to ? ionization of surface OH groups on the octahedral sheets isomorphic substitution of a central atom for another in the crystal structure of the clay coating of the clay surface with Fe and Al oxides ionization of the surface hydroxyl groups on the tetrahedral sheets integration of anions (inner-sphere complexes) into the surface of the clay layer
isomorphic substitution of a central atom for another in the crystal structure of the clay Lec 8 Slide 27: Crystalline clay carry permanent negative charges due to imperfect formation removing the Al or Si to a lower charge
The difference between the wilting point and field capacity is __________. equal to the difference between the saturation point and the field capacity known as the available water capacity always zero the value defined by the leaf area index made up for by the capillary forces of the soil
known as the available water capacity
Which of the following is NOT a characteristic of soil colloids? very small size high external surface area electronegative charges ability to exchange ions with the soil solution low water holding capacity
low water holding capacity Recall: Lecture 8 Slide 22, Semectite an expanding type phyllosilicate, Can hold a large quantiy of water. Moreover, Semectite is common in dry soils. with less weathering Soil colloids are small 1-2 micrometers Given their small size in total they have high external surface area They can have electronagitive charges They do exchange ions with the soil solution in cation exchange
Complete the statement: As an igneous rock weathers in a humid climate, the soil formed has [...]. Lower concentrations of calcium (Ca) and magnesium (Mg) than did the rock. This is because chemical weathering transfers Ca and Mg ions into the soil solution from where they evaporate into the atmosphere. lower concentrations of calcium (Ca) and magnesium (Mg) than did the rock. This is because chemical weathering transfers Ca and Mg ions into the soil solution from where they can be taken up by plant roots or leached into the groundwater. lower concentrations of calcium (Ca) and magnesium (Mg) than did the rock. This is because Ca- and Mg-rich minerals are more resistant to chemical weathering than other components. higher concentrations of calcium (Ca) and magnesium (Mg) than did the rock. This is because chemical weathering turns the Ca and Mg ions into oxides that are highly resistant to further breakdown.
lower concentrations of calcium (Ca) and magnesium (Mg) than did the rock. This is because chemical weathering transfers Ca and Mg ions into the soil solution from where they can be taken up by plant roots or leached into the groundwater.
If you were seeking a soil colloid with a high capacity to adsorb cationic pollutants (e.g. Cu2+), but also with a consistent capacity to do so even as the pH varied from 4.0 to 7.5, which of the following would you choose? montmorillonite kaolinite fine-grained mica chlorite organic matter
montmorillonite Recall: Lec 8 slide 23 Organic is very pH dependant Chlorite is 20% pH dependant (non expanding) Kaolinite is very pH dependant Fine grained mica is 20% pH dependant montmorillonite is a specific type of semectite the greatest 2:1 Expanding type In summary, 2:1 expanding types Semectite and Vermiculite are not pH dependant 5%. 2:1 non expanding crystalline colloids (micas and Chlorites) are semi pH dependant 20% 1:1 kaolinite is 95% pH dependant
Cutting down trees to build housing units results in [ Select ] ["more", "the same amount of", "less"] river discharge and surface erosion because less water is returned to the atmosphere by [ Select ] ["transpiration", "photosynthesis", "percolation", "evaporation"] .
more Transpiration Recall: Transpiration = transpiration into the atmosphere from roots and leaves Percolation = remember infiltration, its after its been infiltrated from precipitation and then percolates through the soil
In cation exchange reactions, hydrated cations adsorbed to the surface of a colloidal particle are replaced by ____________________. other hydrated cations an equivalent number of water molecules an equivalent number of anions covalent bonds shared electrons
other hydrated cations Recall: Lecture 9 Slide 24. Cation exchange happens when colloids swap attached cations with other cations, Following a priority depending on electronegativity. The higher the charge and the smaller the hydrated radius, the stronger the absorption (except H+) See Lec 9 Slide 29
Which is an effective measure to prevent the thaw of permafrost underneath a building? placing the building on stilts to elevate the building above the ground adding a layer of course material (sand, gravel) on the ground directly under and all around the building compacting the topsoil prior to the construction of the building wetting the topsoil prior to the construction of the building using heavier construction materials or taller building to increase the pressure on the soil
placing the building on stilts to elevate the building above the ground
Match the following terms: Percolation Infiltration Watershed Evaporation Surface runoff or discharge rain water wetting the topsoil? water moving through a B horizon toward an aquifer? a flooded street? an area of land drained by a single system of streams? water emitted to the atmosphere from wet surfaces?
rain water wetting the topsoil infiltration water moving through a B horizon toward an aquifer percolation a flooded street (surface) runoff or discharge an area of land drained by a single system of streams watershed water emitted to the atmosphere from wet surfaces evaporation
Forest fires result in sufficiently high soil temperatures to cause the vaporization and movement of organic compounds in soil. Which is the main effect of these compounds? enhance soil structural stability increase pH decrease pH increase soil organic matter content decrease bulk density decrease field capacity reduce infiltration and percolation
reduce infiltration and percolation
Soil colloids are, by definition, ______________. made up of organic (humic) matter made up of mineral matter crystalline in nature negatively charged smaller than 1 or 2 micrometers in diameter
smaller than 1 or 2 micrometers in diameter Recall: There are 2 main types of soil colloids: Organic (1) and Inorganic (3) Inorganic contains crystalline sillicate, noncrystalline, and Fe and Al oxides. They all are 1 or 2 micrometers in diameter
A black, heavy soil (Vertisol) in Texas (semi-arid climate) contains significant amounts of a silicate clay. Which colloid is most likely present? kaolinite smectite fine-grained micachlorite vermiculite
smectite From Lecture 9 slide 12 Recall: Kaolinite and Oxides of Fe and Al are abundant in Tropical conditions, hot wet climates. This is an explination for soil with redish hue. However, the lack of water (semi-arid climate) Is most likely Smectite Moreover, We dont need to know this for midterm 1. Vertisol has a high concentration of Smectite and no vermiculite. Due to the lack of water in a semi-arid climate reducing weathering of primary mineral to form colloids.
The expression, P - ET - D estimates the ________ a watershed. discharge volume from interception in flood risk by surface runoff in soil water content of evaporation from
soil water content of
Which of the following is NOT a major factor in determining the aeration status of a soil? redox potential macropore volume the concentration of nitrogen gas in the soil the concentration of oxygen gas in the soil the concentration of carbon dioxide gas in the soil
the concentration of nitrogen gas in the soil
Alternate freezing and thawing of soils result in "heaving" of plants, the destruction of shallow building foundations, and formation of patterned ground. This is caused primarily by what? the expansion of water when it freezes the hydration and swelling of clay-sized particles pressure from upward movement of water from lower soil horizons compaction by reindeer the physical weathering of soil particles
the expansion of water when it freezes
Under saturated conditions, he flow of water is lower in soils with a greater hydraulic conductivity. there is more water flow through a thinner acquifer than a wider acquifer. the flow of water is greater in soil with a greater hydraulic conductivity. the flow of water is lower at greater water potential gradients.
the flow of water is greater in soil with a greater hydraulic conductivity.
What is salt weathering? the formation of minerals in rock cracks during the evaporation of salty water, forcing rock apart the formation of minerals in rock cracks during the condensation of salty water, forcing rock apart the formation of ice in rock cracks during the condensation of salty water, forcing rock apart the formation of ice in rock cracks during the evaporation of salty water, forcing rock apart
the formation of minerals in rock cracks during the evaporation of salty water, forcing rock apart
Allophane differs from other silicate clays in all ways but one of the following? (select the one) he presence of negative charges on the colloidal particles nature of parent materials from which it forms degree of crystallization of the particles (amorphous vs. crystalline structure) the period of time it has been subject to weathering widespread occurrence around the world
the presence of negative charges on the colloidal particles Recall: Allophane is a primary noncrystalline soil colloid. One of the most common. Lec 8 Slide 35: Similar to organic soil colloids, A noncrystalline soil colloid is very pH dependant. Therefore, It is different from every aspect except the amount of negative charge on its self "colloidal particles". Depending on pH it can have exactly the same abot of negative charges as an crystalline soil colloid.
What is not an indicative feature of a waterlogged soil? the color of the soil is dominated by bluish-grey colors (chroma <1) presence of iron- or manganese-rich nodules the soil has a high clay content presence of high organic matter levels the soil smells of rotten eggs
the soil has a high clay content
The Eh of a soil (pH = 6.5) was reported to be -0.15 volts (-150 mV). This Eh level indicates that ___________. the soil is anaerobic, so that microorganisms are reducing sulfate as electron acceptors instead of oxygen and producing a toxic gas (H2S) that smells like rotten eggs the soil is anaerobic, so that microorganisms are reducing iron as electron acceptors instead of oxygen the soil is anaerobic, so that microorganisms are reducing nitrate or manganese as electron acceptors instead of oxygen the soil is extremely reduced and a likely source of carbon dioxide production and a sink for methane from the atmosphere the soil is well aerated and oxygen is sufficient for root respiration and anaerobic metabolism by bacteria
the soil is anaerobic, so that microorganisms are reducing sulfate as electron acceptors instead of oxygen and producing a toxic gas (H2S) that smells like rotten eggs
The redox potential is a measure of what? molecular oxygen content carbon dioxide content ferric iron (Fe(III)) content the tendency of a substance to accept of donate electrons the balance between hydrogen and hydroxyl ions in solution the soil's color, i.e. chroma (brightness)
the tendency of a substance to accept of donate electrons
The rocky area at the bottom of the photo would be considered which section of a soil profile? organic layer subsoil topsoil unconsolidated material
unconsolidated material
Which statement about soil water is FALSE? volumetric water content can be monitored with tensiometers. volumetric water content can be calculated from multiplying the gravimetric water content with the bulk density of a soil. volumetric water content can be measured with TDR probes. the determination of the gravimetric water content of a soil is a destructive and slow process. gravimetric water content is expressed in kg water / kg soil.
volumetric water content can be monitored with tensiometers.
Under which conditions are the processes of weathering, leaching, and input of organic material from plants into soil maximized? warm temperatures and scarce water cool temperatures and abundant water warm temperatures and abundant water cool temperatures and scarce water
warm temperatures and abundant water
Soils rich in iron oxide are yellowish-brown or reddish. whitish or grayish. blackish. greenish.
yellowish-brown or reddish.
