Questions Multiple-Choice 1) Clay minerals formed from gabbro or diorite bedrock illustrate which kind of weathering? A) chemical B) proactive C) syntropical D) mechanical Answer: A Diff: 1 2) Which of the following is/are most susceptible to chemical weathering by dissolution? A) quartz B) clay minerals C) iron oxides D) calcite Answer: D Diff: 1 3) Frost wedging is the major weathering process contributing to the formation of which regolith material? A) tropical laterites B) talus slopes C) C soil horizons D) mature pedalfers Answer: B Diff: 1 4) What portion of an angular, fracture-bounded granitic block shows the highest rate of weathering? A) the unfractured interior B) the edges and corners C) the crack surfaces not including edges and corners D) All of the above show equal rates. Answer: B Diff: 1 5) Which of the following describes a characteristic process in the formation of a pedalfer soil? A) soil bacteria produce organic acids that precipitate calcium carbonate in the B horizon B) iron oxides and aluminum-rich clays are precipitated in the B horizon C) humus accumulates below the solum in the C horizon D) clays are eluviated upward from the C horizon Answer: B Diff: 1
6) Why is the humus layer typically thicker in a cool, temperate, forest soil than in a tropical rainforest soil? A) Less humus is produced in the tropical rainforest because the B horizon is so poorly developed. B) Less humus is produced in the cool, temperate forest but the rate of decay and oxidation is slower than in a tropical rainforest. C) More humus is produced in the tropical rainforest, but it is quickly washed away by the heavy rains. D) In a tropical rainforest, the forest-floor litter is often burned during the dry season. Answer: B d W F 7) Clay minerals, silica (Si02), and dissolved potassium bicarbonate in the soil water are products of which process? A) chemical weathering of olivine and plagioclase feldspar B) mechanical weathering of granite and rhyolite C) chemical weathering of orthoclase feldspar D) differential mechanical weathering of micas Answer: C Diff: 1 8) What two factors speed up rates of chemical reaction and weathering in rocks and soils? A) low temperatures; very dry B) low temperatures; very moist C) high temperatures; very dry D) warm temperatures; very moist Answer: D Diff: 1 9) In terrain with steep hill slopes, which crop and cultivation technique will minimize soil erosion? A) corn; rows trending straight down the slope, frequent cultivation B) apples; land between the trees is planted in grass and not cultivated C) winter wheat; after the harvest, the field is plowed and left idle until next fall D) bean, rows are spaced wider than on a level field Answer: B Diff: 2 10) In which area are pedocal soils most likely to be found? A) a tropical rainforest in the Amazon Basin of Brazil B) a bitterly cold, permafrost area in north-central Siberia C) a forested area of the southeastern United States D) a moderately dry to semiarid grassland such as the western Great Plains Answer: A
Diff: 1 11) 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 southfacing 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 more moisture and sunlight; rock weathering is slower. C) North-facing slopes receive about the same amount of precipitation as south-facing slopes; less moisture evaporates from north-facing slopes. D) South-facing slopes receive less moisture, yet rock weathering is faster. Answer: C Diff: 2 12) 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) chemical weathering of quartz and feldspars C) precipitation of iron oxides during the chemical weathering process D) mechanical weathering of the feldspars and micas in granite and rhyolite Answer: C Diff: 1 13) Which of the following statements about acidic precipitation is likely to be false? A) Chemical weathering and deterioration of exposed rock and metal surfaces will accelerate if acidic precipitation increases. B) Lowered taxes and relaxed governmental regulations will result in more private and public sector spending to reduce emissions of acid-forming gases to the atmosphere. C) Fish and other aquatic species in acidified lakes will eventually die off and disappear due to the toxic effects of the acidic waters and increased levels of dissolved aluminum. D) Damage to trees and plants, especially to tender new growth, will intensify if acidic precipitation worsens. Answer: B Diff: 1 14) Which of the following statements about laterites or tropical rainforests is true? A) Laterite soils readily compact and hardened when dried and exposed to sunlight. B) Rainforests regenerate quickly following clear cutting or clearing for agriculture. C) Laterite soils are very rich in nutrients required for vigorous plant growth. D) Laterites, with proper management, are very suitable for commercial agriculture. Answer: A Diff: 1 15) Which of the following best describes the "Dust Bowl"? A) the long drought preceding the Irish potato famine of the 1840s
B) the area covered by volcanic ash around Mt. Pinatubo, 1991 C) areas of severe wind erosion on the Great Plains, 1930s D) a New Year's Day invitational soccer match in Tripoli, Libya Answer: C Diff: 1 16) Which one of the following is an important, mechanical weathering process for enlarging fractures and extending them deeper into large boulders and bedrock? A) oxidation B) eluviation C) hydrologic cycling D) frost wedging Answer: D Diff: 1 17) Which of the following best describes sets of fractures in relatively fresh bedrock, such as granite, that are roughly parallel to the land surface? A) thermal expansion cracks B) sheeting fractures C) hydrolytic failures D) columnar joints Answer: B Diff: 1 18) What two, chemical constituents cannot form by chemical weathering of the feldspar minerals? A) soluble sodium and potassium bicarbonates B) insoluble iron oxides and soluble magnesium bicarbonates C) silica and insoluble clay minerals D) silica and soluble calcium bicarbonate Answer: B Diff: 1 19) Under similar warm, moist climatic conditions, why would basalt and gabbro generally have higher chemical weathering rates than rhyolite and granite? A) The quartz in the gabbro and basalt decomposes very quickly. 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 potassium feldspars and quartz in the rhyolite and granite are more susceptible to cracking by frost wedging. Answer: B Diff: 2
20) Which one of the following statements concerning mechanical weathering is not true? A) reduces grain sizes of rock particles B) allows for faster rates of chemical weathering C) is important in the formation of talus slopes D) involves a major change in the mineral composition of the weathered material Answer: D Diff: 1 21) Which term describes a soil formed by weathering of the underlying bedrock? A) transformational B) residual C) relict D) transported Answer: B Diff: 1 22) Which one of the following statements best describes erosion? A) disintegration and decomposition of rocks and minerals at the surface B) movement of weathered rock and regolith toward the base of a slope C) the process by which weathered rock and mineral particles are removed from one area and transported elsewhere D) the combined processes of leaching, eluviation, and mass wasting Answer: C Diff: 1 23) Which term best describes those processes that move weathered rock materials and soils downslope? A) podzolization B) slope sheeting C) mass wasting D) talus transfer Answer: C Diff: 1 24) Assume that water filling a crack in a rock undergoes cycles of freezing and melting. Which of the following statement is true? A) Water expands as it melts, causing the crack walls to be pushed apart. B) Water shrinks as it freezes, causing the crack walls to be drawn closer together. C) Water expands as it freezes, causing the crack walls to be pushed apart. D) Water shrinks as it melts, causing the crack walls to be pulled closer together. Answer: C Diff: 1 25) Which of the following best describe the A soil horizon?
A) regolith zone B) erosion zone C) residual zone D) leaching zone Answer: D Diff: 1 26) What mineral particles are the dominant coloring agents in reddish, brownish, and yellowish soils? A) soluble potassium and sodium bicarbonates B) humus and calcium carbonate C) very fine-sized, silica and calcite particles D) dust-sized grains of iron oxides Answer: D Diff: 1 27) Which term best describes an accumulation of angular rock fragments at the base of a steep, bedrock slope or cliff? A) trellis slope B) taliche slope C) tellus slope D) talus slope Answer: D Diff: 1 28) In which area would weathering by frost wedging probably be most effective? A) in a moist, tropical forest B) in cool high desert areas C) where the subsoil is permanently frozen D) in moist, temperate Answer: climates D Diff: 1 29) Which one of the following statements concerning soil erosion is not true? A) Sheet erosion, rills, and gullies develop mainly during prolonged droughts. B) Soils form naturally by weathering; if protected from erosion, sound management can maintain or enhance their nutrient levels and textural characteristics. C) Rates of soil erosion exceed rates of soil formation in some parts of the world. D) Grasses and other vegetation, windbreaks, and contour cropping will help reduce losses of soil from cultivated lands. Answer: A Diff: 1 30) Lateritic soils form under what climatic conditions? A) warm and moist as in a wet, tropical forest B) cool and relatively dry as in the northern Great Plains of the United States
C) hot and dry as in the desert regions of North Africa and Arabia D) moist and temperate as in the northeastern United States Answer: A Diff: 1 31) Which of the following statements concerning humus is not true? A) is typically found above the B soil horizon B) consists of decaying and partly decayed leaves and other plant materials C) is readily leached from the B horizon in weakly acidic, soil solutions D) is less abundant in wet, tropical, forested areas than in temperate, forested areas Answer: C Diff: 1 32) Which of the following statements concerning lateritic soils is generally not true? A) They form in warm, moist, tropical climates. B) They are mainly red in color. C) They remain highly productive agriculturally without additions of fertilizers. D) They consist of only the most insoluble, soil-forming minerals such as iron oxides, aluminum oxides, and clays. Answer: C Diff: 1 33) Caliche is an excessive accumulation of __________. A) calcite in the E horizon of a pedalfer B) clays in the A horizon of a laterite C) clays in hardpan layers of a pedocal D) calcium carbonate in the B horizon of a pedocal Answer: D Diff: 1 34) Which of the following best describes the process of eluviation? A) removal of very fine-sized silt and clay particles from the A and E soil horizons B) buildup of calcite in the B horizon of pedocal soils C) removal of soluble chemical constituents from the A and B soil horizons D) feldspar decomposition and leaching of the soluble products from the C soil horizon Answer: A Diff: 1 35) From the land surface downward to the unweathered bedrock, which of the following is the correct order of the different soil horizons? A) 0, A, E, B, C, bedrock B) A, B, C, D, E, bedrock C) E, A, B, C, 0, bedrock D) D, E, C, B, A, bedrock Answer: A
Diff: 1 Word Analysis Questions Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern. 1) A) frost wedging B) mass wasting Answer: B Diff: 1 2) A) oxidation Answer: D Diff: 1 3) A) surface area Answer: C Diff: 1 4) A) topography Answer: D Diff: 1 5) A) C horizon Answer: A Diff: 1 True/False Questions 1) Quartz weathers readily to aluminum-rich clay minerals. Answer: FALSE Diff: 1 2) Abundant moisture and warm temperatures result in high rates of chemical weathering. Answer: TRUE Diff: 1 3) Very fine-grained, iron oxide particles account for nearly all red, yellow, and brown soil colors. Answer: TRUE Diff: 1 44) In pedalfer soils, the B horizon is enriched in calcite and humus. Answer: FALSE Diff: 1 C) sheeting D) oxidation
B) dissolution C) hydrolysis D) sheeting B) rock characteristicsC) geologic age D) climate
B) time
C) parent material
D) elevation
B) A horizon C) E horizon D) B horizon
5) Pedocal soils typically form by intense chemical weathering under very cold and wet climatic conditions. Answer: FALSE Diff: 1 6) Pedalfers form more readily than pedocals under conditions of low soil moisture content. Answer: FALSE Diff: 1 7) Oxidation of iron is an important chemical weathering process for ferromagnesian silicate minerals like olivine and biotite. Answer: TRUE Diff: 1 8) Sheeting is mainly a process of mechanical weathering. Answer: TRUE Diff: 1 9) Sheeting fractures and exfoliation domes commonly develop in areas with soft, highly fractured bedrock. Answer: TRUE Diff: 1 10) Quartz is quite resistant to weathering and is an important component of sands in riverbeds and on beaches. Answer: TRUE Diff: 1 11) Feldspars commonly decompose during weathering to clay minerals, silica, and soluble constituents. Answer: TRUE Diff: 1 12) Humus is a concentration of decaying, organic matter in the B horizons of lateritic soils. Answer: FALSE Diff: 1 13) Calcite, a major component of some monumental and building stones, slowly dissolves in weakly acidic waters. Answer: TRUE Diff: 1 14) Like most other liquids, water decreases in volume when it freezes. Answer: FALSE
Diff: 1 15) Chemical weathering in bedrock below the land surface often begins along joints and sheeting fractures. Answer: TRUE Diff: 1 16) Removal of soluble chemical constituents from a soil is termed leaching. Answer: TRUE Diff: 1 17) The material caliche represents an extensive, concrete-like accumulation of calcite in the B horizon of a pedalfer soil. Answer: FALSE Diff: 1 18) The solum or true soil includes all horizons above the C horizon. Answer: TRUE Diff: 1 19) Ferromagnesian minerals (like olivine and pyroxene) that crystallize at high temperatures in Bowen's reaction series are generally much less susceptible to chemical weathering than quartz. Answer: FALSE Diff: 1 20) Decomposition of pyrite is an important factor in generating acidic mine drainage. Answer: TRUE Diff: 1 Short Answer Questions 1) What kind of weathering involves only a reduction in the sizes of bedrock, regolith, and mineral particles? Answer: mechanical Diff: 1 2) Half Dome in Yosemite National Park, California, and Stone Mountain in Georgia, are shaped mainly by what mechanical weathering process? Answer: sheeting Diff: 1 3) Which form of chemical weathering specifically affects the iron contained in ferromagnesian, rock-forming, silicate minerals? Answer: oxidation
Diff: 1 4) What is the most abundant, naturally produced, weak acid involved in chemical weathering and soil formation? Answer: carbonic Diff: 1 5) The very fine-sized, clay mineral particles move downward from the A to the B horizon of some soils. What is this process called? Answer: eluviation Diff: 1 6) Under most weathering conditions, which mineral component of granites and rhyolites would be most resistant to decomposition? Answer: quartz Diff: 1 7) What term describes the layer of partly decayed plant matter at the top of the soil profile in most forested areas? Answer: humus Diff: 1 8) What term refers to removal of soluble constituents from soils? Answer: leaching Diff: 1 9) Which term denotes the true soil above the zone of partly weathered bedrock? Answer: solum Diff: 1 10) What term describes a soil that has developed from silt and clay deposited by a flooding river? Answer: transported Diff: 1 11) Would you call the loose, unconsolidated, surface material on Mars regolith or soil? Answer: regolith Diff: 1 Critical Thinking Questions Use complete sentences, correct spelling, and the information presented in Chapter 6 to answer the questions below 1) Would mechanical or chemical weathering be significant processes on the Moon or another planet in our solar system? Why or why not? Name at least two characteristics or factors here on Earth that allow for weathering to be a significant geologic process.
Diff: 2 2) Compare and contrast soil formation between an arid region underlain by quartz sandstone and a temperate climate in an area composed of granite. Include a discussion of the major factors influencing soil formation and the role of each in both regions. Diff: 3 3) As a geologist employed by an engineering firm, your first assignment is to assess the potential for soil erosion on a 2000-acre site. There has been no previous development on the property, which consist of roughly equal portions of farmland, forests that have recently been cut down, and hilly terrain with native vegetation. Briefly outline your approach for assessment including what factors are important for you study, which areas have a higher potential for erosion problems, and what steps you might suggest to prevent or lessen soil erosion. Diff: 3 Visualization Questions 1) What process does the diagram below illustrate?
Answer: sheeting Diff: 1 2) What is the feature labeled "A" in the diagram below? Also, how did it form?
Answer: talus slope. Rocks fell from the adjacent rocky cliff and accumulated at the base of the cliff as a talus slope. Diff: 1 3) Carefully examine the illustration below and the features labeled A through D.
Give a letter (A, B, C, or D) for each answer below. At which location would the thickest residual soil develop? (a) __________ At which location would the greatest amount of frost wedging occur? (b) __________ At which location would the thickest transported soil develop? (c) __________ At which location would there be the most unconsolidated deposits? (d) __________ Answer: (a) D (b) A (c) B (d) B
Diff: 2 4) Fill in the blanks on the diagram below with the names of the soil "layers" that are labeled.
Answer: (a) O horizon horizon Diff: 1
(b) A horizon
(c) B horizon
(d) C