Chapter 6 Short Answer
1. Mechanical weathering produces no change in the chemical composition of the parent rock.
T
10. Laterite soils are typical of rainforests.
T
11. Laterite soils are the product of intense leaching.
T
14. A soil that is rich in clay and expands by more than 6% is an expansive soil.
T
2. Pressure release is a mechanical weathering process that occurs often in intrusive rocks such as those formed in batholiths.
T
4. Salt crystals can exert enough force to widen cracks and dislodge particles in some rocks.
T
5. Sheet joints, created by pressure release, form roughly parallel to the rock surface.
T
8. Laterite soils are not very fertile.
T
16. On a pH scale, the pH value of something neutral is _______; the pH of normal rain is _____ and acid rain is less than _____.
7; 5.6; 5.0
1. What is erosion? a. movement of weathered material from its source site b. decomposition of rock c. disintegration of rock d. weathering of rock and transportation of sediment e. disintegration of soil
A
20. The biggest problem areas for acid rain include a. the eastern United States and much of Europe. b. China and Australia. c. western Europe and the western United States. d. the Amazon, Congo and Pacific rainforests.
A
14. Carbonic acid forms from the combination of a. water and bicarbonate ion. b. water and carbon dioxide. c. carbon dioxide and hydrogen ion. d. calcium ion and bicarbonate ion.
B
17. Humus ____. a. is the material always comprising the topmost soil horizon b. is dark, organic-rich material formed by bacterial decay c. is leaf-litter d. must include sediments e. none of these
B
18. What is caliche? a. a layer of silica cement within a pedalfer b. a layer of precipitated calcium carbonate in horizon B c. a layer of rock between soil layers C and D d. a deposit formed in alkali soils e. a light colored layer of unstable minerals
B
15. Hydrolysis is the chemical reaction between a mineral's ions and a. water molecules. b. hydrogen and oxygen ions. c. hydrogen and hydroxyl ions. d. hydroxide ions.
C
10. What is a source of carbon dioxide for carbonic acid? a. the atmosphere b. soil c. groundwater d. surface water e. all of these
E
11. Hydrolysis is particularly effective in weathering ____. a. limestone b. sandstone c. quartz d. calcite e. feldspar
E
13. Which of the following is not a factor influencing the rate of chemical weathering? a. climate b. particle size c. parent material d. humidity e. gravity
E
12. The most stable shape a stone can form is a rectangle.
F
18. What factors lead to the development of the "Dust Bowl" during the 1930s in the United States?
Farming resulted in the loss of natural soil cover; improper farming practices resulted in increased soil erosion; and drought exacerbated the soil erosion.
7. In what climatic conditions is frost action most effective?
Frost action is most effective in areas where temperatures fluctuate commonly above and below freezing.
7. ____________________ is an essential component of soil as it provides nutrients to plants and increases the ability of the soil to retain ____________________.
Humus, moisture
13. Briefly explain how hydrolysis results in the weathering of some minerals.
In hydrolysis, hydrogen ions replace positive ions in minerals and the released mineral ions go into solution, changing the mineral's composition.
4. How does mechanical weathering differ from chemical weathering?
In mechanical weathering, physical forces break the rock materials into smaller pieces that retain their chemical composition; in chemical weathering the composition is altered.
12. Carbon dioxide levels in the atmosphere are rising due to the burning of fossil fuels. How might this increased level of carbon dioxide affect rates of weathering?
Increased amounts of atmospheric carbon dioxide will increase the amount of carbonic acid that forms in the atmosphere and result in an increase of chemical weathering.
5. Name an important physical property about water that makes it unique among liquids, and why is this property important in the weathering of rocks?
It increases in volume when it freezes (changes from a liquid to a solid state). The expanding volume creates pressures which may break rocks and minerals into smaller pieces.
11. How does mechanical weathering aid chemical weathering?
Mechanical weathering produces smaller particles, with more surface area for the given volume, and chemical weathering operates on the surface of the material.
13. ____________________ erosion occurs when water carves small channels into a soil bed.
Rill
14. How does regolith differ from soil?
Regolith is unconsolidated rock material that covers the land surface. Soil is regolith that includes weathered material, water, air, organic matter, (and can support plant growth).
16. What is soil degradation?
Soil degradation includes any soil losses that exceed the rate of soil formation, any decrease in soil fertility, or loss of soil by erosion.
2. How does weathering differ from erosion?
Weathering is the breakdown of material in place; erosion is the removal of the weathered materials.
1. Define weathering.
Weathering is the physical disintegration and/or chemical decomposition of rocks at or near Earth's surface as they are exposed to the atmosphere, hydrosphere, and/or biosphere.
5. Carbonate minerals, like calcite, dissolve readily in a solution that is _______.
acidic
15. The economically valuable mineral resource produced by intense chemical weathering that is found only in laterite soils is called ____________________.
bauxite aluminum ore
12. The most important factor controlling soil formation is ____________________.
climate
17. What three types of soil degradation are recognized?
erosion, chemical deterioration, and physical deterioration
2. Large, rounded masses of rock from which joint-bounded slabs of rock have slipped off are _______ _______.
exfoliation domes
6. List some examples of mechanical weathering processes.
frost action/pressure release/thermal expansion and contraction/salt crystal growth/activities of organisms
9. Soils that are a result of intense weathering and are typically found in the tropics are ____________________.
laterite
10. Because quartzite is (more/less) ____________________ chemically stable than granite, it will be covered by a (thicker/thinner) ____________________ layer of soil than will an adjacent body of granite.
more, thinner
3. The chemical weathering process that produces most of the red, yellow, and brown colors seen in soils and many sedimentary rocks is called ____________________.
oxidation
9. What are the major factors that control the rate of chemical weathering?
presence of fractures, particle size, climate, parent material
8. A(n) ____________________ soil forms where the parent material has weathered, whereas ____________________ soil develops from eroded material that was weathered at another location.
residual, transported
1. Weathering is an essential part of the _______ _______ because parent material must break down into smaller pieces or perhaps dissolve to become sediment.
rock cycle
14. The actions of ____________________ and ____________________ are responsible for most soil erosion.
wind, water water, wind
10. Why do small particles weather more rapidly than large particles?
Chemical weathering occurs on the surface of a rock or mineral, and small particles have larger surface areas per given volume.
9. Thermal expansion and contraction occur most commonly in which of the following conditions? a. cold and hot b. arid and cold c. humid and hot d. arid and hot e. humid and cold
A
9. Laterite soils can support extended periods of farming.
F
11. Under similar climatic conditions, soil will develop (faster/slower) ____________________ on solid bedrock than it will on unconsolidated sediment.
slower
19. Any process that removes soil or makes it less productive is called _______ _______.
soil degradation
4. Three important chemical processes involved in chemical weathering are ____________________, ____________________, and ____________________.
solution, oxidation, hydrolysis
3. List some ways in which organisms contribute to mechanical weathering.
burrowing/particle mixing/root wedging/reduction of particle size
8. How can organisms contribute to chemical weathering?
by the removal of ions from soil water; release of organic acids
6. The process that decomposes rocks and minerals by altering the makeup of the parent material is called _______ _______.
chemical weathering
15. What are the principle controls on soil formation?
climate, parent material, organic activity, relief (and slope), time
12. The important weathering product(s) of hydrolysis of feldspar is (are) ____. a. ferromagnesian minerals b. sand minerals c. dissolved calcium d. clay minerals e. accessory minerals
D
19. In soil, the A horizon is a. low in organic matter. b. the site of little biological activity. c. full of sand and gravel. d. composed mostly of clays and stable minerals.
D
7. Under which conditions does pressure release occur? a. humid and seasonal b. hot and arid c. cold and humid d. where there is uplift and erosion e. where there is faulting and seismic activity
D
8. What does pressure release weathering result in? a. sheet jointing b. rock bursts c. exfoliation d. exfoliation domes e. all of these
D
4. Which of the following contribute to weathering? a. organisms such as worms, bacteria, and trees b. oxygen and carbon dioxide in the air c. rain water d. organic acids e. all of these
E
5. Which of the following is a means of mechanical weathering? a. frost wedging b. pressure release c. thermal expansion and contraction d. burrowing and root wedging e. all of these
E
13. Acid rain is a problem in regions near the source of the emissions but, unlike global warming, it is not a worldwide problem.
F
3. Thermal expansion and contraction occur because rock is an excellent conductor of heat.
F
6. A rock may be subjected to either mechanical or chemical weathering but never both at the same time.
F
7. Laterite soils are rich in organic matter.
F
2. Weathering that takes place at different rates even in the same area is called a. mechanical weathering. b. differential weathering. c. chemical weathering. d. original weathering.
B
6. Frost wedging in the mountains produces which type of material? a. tailings b. talus c. conglomerate d. exfoliation e. regolith
B
16. Clay particles in soil are important to soil development because ____. a. They hold soil particles apart. b. They allow water and gases to enter soil. c. They retain water and supply nutrients. d. They allow the flow of groundwater. e. They drain poorly.
C
3. Weathering is classified into which of the following categories? a. mechanistic and compositional b. mechanical and physical c. chemical and physical d. physical and chemical e. organic and inorganic
C