Deck 6: Weathering and Soils

Question 1

In the Rocky Mountain region of the United States, north- facing slopes (downhill direction is toward the north)are typically more moist and heavily forested than south- facing slopes. Why?

A)North- facing slopes receive more sunlight in the summer; snow melts faster and more soil moisture is available for the trees.
B)South- facing slopes receive less moisture, yet rock weathering is faster.
C)South- facing slopes receive more moisture and sunlight; rock weathering is slower.
D)North- facing slopes receive about the same amount of precipitation as south- facing slopes; less moisture evaporates from north- facing slopes.

Answer 1

D

Question 2

Which of the following best describes the process of eluviation?

A)removal of very fine- sized silt and clay particles from the E soil horizon
B)buildup of calcite in the B horizon of pedocal soils
C)feldspar decomposition and leaching of the soluble products from the C soil horizon
D)removal of soluble chemical constituents from the A and B soil horizons

Answer 2

A

Question 3

Which term best describes an accumulation of angular rock fragments at the base of a steep, bedrock slope or cliff?

A)talus slope
B)taliche slope
C)trellis slope
D)tellus slope

Answer 3

A

Question 4

Which term describes a soil formed by weathering of the underlying bedrock?

A)transported
B)relict
C)transformational
D)residual

Question 5

Which one of the following statements concerning mechanical weathering is NOT true?

A)It is important in the formation of talus slopes.
B)It involves a major change in the mineral composition of the weathered material.
C)It allows for faster rates of chemical weathering.
D)It reduces grain sizes of rock particles.

Question 6

Which of the following statements about oxisols in tropical rainforests is TRUE?

A)Oxisols, with proper management, are very suitable for commercial agriculture.
B)Oxisol soils readily compact and harden when dried and exposed to sunlight.
C)Rainforests regenerate quickly following clear cutting or clearing for agriculture.
D)Oxisol soils are very rich in nutrients required for vigorous plant growth.

Question 7

Which one of the following is an important, mechanical weathering process for enlarging fractures and extending them deeper into large boulders and bedrock?

A)eluviation
B)hydrologic cycling
C)oxidation
D)frost wedging

Question 8

Which of the following best describes the E soil horizon?

A)leaching zone
B)residual zone
C)erosion zone
D)regolith zone

Question 9

The finely divided, red, brown, and yellow soil- coloring minerals originate by what process?

A)mechanical weathering of very fine- grained, blue- gray clays
B)mechanical weathering of the feldspars and micas in granite and rhyolite
C)precipitation of iron oxides during the chemical weathering process
D)chemical weathering of quartz and feldspars

Question 10

Which one of the following statements concerning soil erosion is NOT true?

A)Grasses and other vegetation, windbreaks, and contour cropping will help reduce losses of soil from cultivated lands.
B)Sheet erosion, rills, and gullies develop mainly during prolonged droughts.
C)Soils form naturally by weathering; if protected from erosion, sound management can maintain or enhance their nutrient levels and textural characteristics.
D)Rates of soil erosion exceed rates of soil formation in some parts of the world.

Question 11

Which of the following statements concerning oxisol soils is generally NOT true?

A)They remain highly productive agriculturally without additions of fertilizers.
B)They are mainly red in color.
C)They consist of only the most insoluble, soil- forming minerals.
D)They form in warm, moist, tropical climates.

Question 12

Which one of the following statements best describes erosion?

A)Erosion is the disintegration and decomposition of rocks and minerals at the surface.
B)Erosion is the process by which weathered rock and mineral particles are removed from one area and transported elsewhere.
C)Erosion is the movement of weathered rock and regolith toward the base of a slope.
D)Erosion is the combined processes of leaching, eluviation, and mass wasting.

Question 13

What two factors speed up rates of chemical reaction and weathering in rocks and soils?

A)high temperatures; very dry
B)low temperatures; very dry
C)warm temperatures; very moist
D)low temperatures; very moist

Question 14

Which of the following best describes the "Dust Bowl"?

A)the area covered by volcanic ash around Mt. Pinatubo, 1991
B)a New Year's Day invitational soccer match in Tripoli, Libya
C)areas of severe wind erosion on the Great Plains, 1930s
D)the long drought preceding the Irish potato famine of the 1840s

Question 15

What mineral particles are the dominant coloring agents in reddish, brownish, and yellowish soils?

A)dust- sized grains of iron oxides
B)humus and calcium carbonate
C)soluble potassium and sodium bicarbonates
D)very fine- sized, silica and calcite particles

Question 16

From the land surface downward to the unweathered bedrock, which of the following is the correct order of the different soil horizons?

A)D, E, C, B, A, bedrock
B)O, A, E, B, C, bedrock
C)A, B, C, D, E, bedrock
D)E, A, B, C, O, bedrock

Question 17

What portion of an angular, fracture- bounded granitic block shows the highest rate of weathering?

A)the unfractured interior
B)the crack surfaces not including edges and corners
C)the edges and corners
D)All of the above show equal rates.

Question 18

Frost wedging is the major weathering process contributing to the formation of which regolith material?

A)soil horizons
B)talus slopes
C)tropical laterites
D)mature pedalfers

Question 19

Oxisol soils form under what climatic conditions?

A)cool and relatively dry as in the northern Great Plains of the United States
B)moist and temperate as in the northeastern United States
C)warm and moist as in a wet, tropical forest
D)hot and dry as in the desert regions of North Africa and Arabia

Question 20

Which of the following statements concerning humus is NOT true?

A)Humus consists of decaying and partly decayed leaves and other plant materials.
B)Humus is typically found above the B soil horizon.
C)Humus is less abundant in wet, tropical, forested areas than in temperate, forested areas.
D)Humus is readily leached from the B horizon in weakly acidic, soil solutions.

Question 21

Assume that water filling a crack in a rock undergoes cycles of freezing and melting. Which of the following statement is TRUE?

A)Water shrinks as it freezes, causing the crack walls to be drawn closer together.
B)Water expands as it freezes, causing the crack walls to be pushed apart.
C)Water shrinks as it melts, causing the crack walls to be pulled closer together.
D)Water expands as it melts, causing the crack walls to be pushed apart.

Question 22

What kind of weathering involves only a reduction in the sizes of bedrock, regolith, and mineral particles?

Question 23

What term describes the layer of partly decayed plant matter at the top of the soil profile in most forested areas?

Question 24

What two chemical constituents cannot form by chemical weathering of the feldspar minerals?

A)silica and insoluble clay minerals
B)silica and soluble calcium bicarbonate
C)insoluble iron oxides and soluble magnesium bicarbonates
D)soluble sodium and potassium bicarbonates

Question 25

What term refers to removal of soluble constituents from soils?

Question 26

Half Dome in Yosemite National Park, California, and Stone Mountain in Georgia, are shaped mainly by what mechanical weathering process?

Question 27

Which of the following best describes sets of fractures in relatively fresh bedrock, such as granite, which are roughly parallel to the land surface?

A)thermal expansion cracks
B)sheeting fractures
C)columnar joints
D)hydrolytic failures

Question 28

Which of the following is/are most susceptible to chemical weathering by dissolution?

A)clay minerals
B)iron oxides
C)calcite
D)quartz

Question 29

What process does the diagram below illustrate?

Question 30

Based on the examples and discussion in chapter 6, what is the relationship of climate to weathering, both chemical and mechanical? Also, are certain climates more susceptible to certain types of weathering? Why or why not?

Question 31

Would you call the loose, unconsolidated, surface material on Mars regolith or soil?

Question 32

Clay minerals, silica (SiO2), and dissolved potassium bicarbonate in the soil water are products of which process?

A)chemical weathering of orthoclase feldspar
B)differential mechanical weathering of micas
C)chemical weathering of olivine and plagioclase feldspar
D)mechanical weathering of granite and rhyolite

Question 33

Briefly discuss the classification of soils. What parameters are important? What characteristics or features are evaluated for distinguishing between different types of soils?

Question 34

Clay minerals formed from gabbro or diorite bedrock illustrate which kind of weathering?

A)chemical
B)syntropical
C)mechanical
D)proactive

Question 35

Which term denotes the true soil above the zone of partly weathered bedrock?

Question 36

What is the most abundant, naturally produced, weak acid involved in chemical weathering and soil formation?

Question 37

Under most weathering conditions, which mineral component of granites and rhyolites would be most resistant to decomposition?

Question 38

Under similar warm, moist climatic conditions, why would basalt and gabbro generally have higher chemical weathering rates than rhyolite and granite?

A)The potassium feldspars and quartz in the rhyolite and granite are more susceptible to cracking by frost wedging.
B)The ferromagnesian minerals in the gabbro and basalt are subject to oxidation and chemical breakdown.
C)The plagioclase feldspars in the granite and rhyolite decompose readily to clay minerals and iron oxides.
D)The quartz in the gabbro and basalt decomposes very quickly.

Question 39

The very fine- sized, clay mineral particles move downward from the A to the B horizon of some soils. What is this process called?

Question 40

In which area would weathering by frost wedging probably be most effective?

A)in cool high desert areas
B)where the subsoil is permanently frozen
C)in moist, temperate climates
D)in a moist, tropical forest

Question 41

How do weathering and the development of soils influence the topography and landforms in a given region? Are certain landforms indicative of the particular bedrock geology of a region or is that determined more by weathering?