Name: ______

Geology Chapter 5 – Weathering, Soil, and Mass Movement

MichaelWysesslonWashingtonUniversity

Big Ideas As fast as plate tectonics can create land, weathering destroys it. The ultimate energy source of weathering is the sun, though its major agent is water. It could be said that the first law of geology is that rocks fall downhill. This occurs as mass movements, which are driven by Earth's gravitational attraction.

Space and Time The entire surface of continents is slowly being destroyed through a combination of mechanical and chemical weathering. Mechanical weathering primarily occurs by frost wedging, unloading (pressure release), and the activities of plants and animals. Chemical weathering occurs though reactions involving water and materials dissolved within it. The rates of weathering are highly variable, and depend upon regional rock types and climate.

Forces and Motion Mass movements involve portions of the ground moving downhill together. They take many different forms, including rockfalls, slides, slumps, flows, and creep. Mass movements can be triggered by too much or too little water, oversteepened slopes, or the occurrence of earthquakes.

Matter and Energy Weathering of rock results in the production of soil, which is vital for human existence because it supports plant life. Soil contains a mixture of mineral matter (in differing amounts of sand, silt, and clay), organic matter, water, and air. Soil develops from the top down, and varies greatly depending upon the type of parent rock and regional climate.

Earth as a System Chemical weathering occurs more rapidly when rain water is acidic, so the formation of acid rain through human industrial activities has greatly increased weathering in some parts of the world.

Section 1 – Weathering

  1. What is Earth’s surface doing?
  2. What are the two types of weathering?
  3. What is mechanical weathering?
  4. Does each new piece have the same characteristics of the original rock?
  5. What are the three physical processes that are responsible for mechanical weathering in nature?
  6. What is frost wedging and what causes it?
  7. What is talus and where does it usually form?
  8. What is unloading and what does it cause?
  9. Describe what exfoliation is.
  10. The activities of ______, including plants, animals, and humans can cause mechanical weathering.
  11. What is chemical weathering?
  12. What is the most important agent of chemical weathering?
  13. Water promotes chemical weathering by absorbing ______from the atmosphere and ground. These dissolved substances then ______react with certain minerals.
  14. What is iron oxide?
  15. How does carbonic acid form?
  16. What is the effect of acid rain?
  17. Chemical weathering can change the ______shape of rock as well as its ______composition.
  18. What is the difference between spheroidal weathering and unloading?
  19. What two factors other than mechanical and chemical weathering affect the rate of weathering of rocks?
  20. Physical characteristics of rock, such as ______, are important in weathering because they influence the ability of water to penetrate the rock.
  21. Climate factors, especially ______and ______, have a strong effect on the rate of weathering.
  22. Describe differential weathering.

Section 2 – Soil

  1. What is regolith and where can it be found?
  2. What is soil?
  3. List the three important characteristics of soil.
  4. What are the four major components of soil?
  5. In most soils, ______matter or ______is an essential component because it is an important source of plant nutrients and increases the soil’s ability to retain ______.
  6. What does soil texture refer to?
  7. The U.S. Department of Agriculture has established categories based on the percentages of ______, silt, and ______in soil.
  8. What strongly influences a soil’s ability to support plant life?
  9. What type of soils are best for plant growth and why?
  10. What does soil structure determine?
  11. What are the most important factors in soil formation?
  12. What is parent material?
  13. The soil that forms on bedrock is called ______soil.
  14. The soil that forms on unconsolidated deposits is called ______soil because its parent material was ______from another location by ______, water, ______, or ______.
  15. In what two ways does the nature of the parent material influence soils?
  16. The longer a soil has been forming, the ______it becomes.
  17. Which factor has the greatest effect on soil formation?
  18. Variations in temperature and ______influence the rate, ______, and type of weathering.
  19. The amount of ______also influences soil fertility by affecting the rate at which ______are removed from the soil.
  20. Scientists name some soils based on the soil’s ______vegetation.
  21. ______are the main source of ______matter in soil.
  22. Microorganisms, including ______, bacteria, and single-celled ______, play an active role in decomposing dead plants and animals.
  23. How do burrowing animals affect soils?
  24. On steep slopes, ______is accelerated.
  25. How does the direction a slope faces affect soil formation?
  26. Although there are ______separate factors that affect soil formation, they all work ______to form soil.
  27. How does soil vary at different depths?
  28. What are soil horizons?
  29. What is a soil profile?
  30. Describe the A horizon.
  31. Describe the B horizon.
  32. Describe the C horizon.
  33. Name the three common types of soil.
  34. Where do pedalfers form and what do they contain to make them red-brown colored?
  35. Where are pedocals found and what do they contain to make them light gray-brown?
  36. Where do laterites form and what makes them a distinctive orange or red color?
  37. What happens when laterite is dried?
  38. Why do the soils in rain forests contain very little nutrients?
  39. How does water erode soils?
  40. Describe the relationship between sheet erosion, rills, and gullies.
  41. How have human activities affected the rate of erosion?
  42. How can scientists estimate the rate of erosion?
  43. What happened during the 1930’s in the Great Plains?
  44. What happens to reservoirs that fill with sediment that has been eroded from soils.
  45. What is the effect of agricultural pesticides and fertilizers on lakes?
  46. List some measures to protect land from erosion.

Section 3 – Mass Movement

  1. Describe mass movement.
  2. What combination produces most landforms?
  3. What are the most common Earth landforms?
  4. Name four factors that commonly trigger mass movements.
  5. How do rains and rapid melting of snow trigger mass movement?
  6. At what angle of slope will soil particles generally stay on the slope.
  7. What happens when the slope is greater than the stable angle?
  8. What do plant roots do for soils and what is the effect of removing vegetation on a soil?
  9. ______are one of the most dramatic triggers of mass movement.
  10. How do geologists classify mass movements?
  11. When does a rockfall occur?
  12. In a slide, a ______of material moves suddenly along a ______, inclined surface.
  13. What is a rockslide?
  14. Which type of mass movement is the fastest?
  15. A ______is the downward movement of a block of material along a curved surface.
  16. What do slumps leave on the cliff?
  17. What are flows?
  18. What is the difference between mudflows and Earthflows?
  19. What is the slowest type of mass movement?
  20. What is one factor that contributes to creep?