Download Weathering, Soil, and Erosion Study Guide

Weathering, Soil, and Erosion Study Guide
1. Define upward expansion.
a. Rock is lifted up and the rocks above it are worn away. The rocks form sheets and break off
(exfoliation).
2. Define erosion and give an example of how this occurs.
a. The removal and transport of materials by natural agents such as wind and running water.
b. Ex: A river carries silt to the ocean.
3. Describe the difference between chemical and mechanical weathering.
a. Chemical – rock’s minerals are changed into different substances.
b. Mechanical – rock is split or broken into smaller pieces of the same material without changing its
composition.
4. Give an example of chemical weathering.
a. Acid rain – sulfur dioxide, nitrogen compounds, and carbon dioxide react with air
b. Carbonic acid – underground caverns form
c. Hydrolysis – form clay minerals
5. Give an example of mechanical weathering.
a. Frost wedging – water freezes in cracks in rocks
b. Wetting and drying – clay swells when wet and shrinks when dry
c. Abrasion – moving rocks scrape against each other
d. Plants and animals – roots expand, animals burrow
6. Why and how does frost wedging occur?
a. Water occupies 10% more space when it freezes, therefore puts pressure on the container (rocks) and
pushes the rock apart.
7. What causes acid rain?
a. Sulfur dioxide, nitrogen compounds, and carbon dioxide react with air.
8. Define residual soil.
a. Parent material is the bedrock beneath the soil
9. Describe different ways that soil erosion can be reduced.
a. Windbreaks – lines of trees planted along the edges of fields
b. Contour farming – plant crops parallel to land contours
c. Terraces – flatten a slope to slow speed of runoff
d. Strip cropping – alternate rows of crops
e. No-till – plowing, planting, weeding, fertilizing is all done at once
10. Define talus and describe where you would expect to find it.
a. Rock fragments weathered from a cliff that have fallen due to gravity.
b. Found at the base of a rocky cliff
11. Differentiate between mudflow and earthflow.
a. Earthflow – mass of weathered material saturated with water flows downhill
b. Mudflow – rapid movement of water that contains large amounts of clay and silt
12. Define and explain the cause of mass movements.
a. Downward transportation of weathered materials by gravity
13. What causes erosion?
a. Climate, rock composition, erosion vs. uplift
b. Agents of erosion: ice, water, wind
14. What causes soil depletion?
a. Occurs when the soil gradually becomes so lacking in nutrients that it can no longer be used to grow a
usable crop
15. Draw a sketch of a soil profile. Label the three horizons. Which is the layer with the greatest humus content
and which is the layer where soluble materials accumulate?
16. Describe the weathering process of wetting and drying.
a. Rock materials expand and shrink as they go from wet to dry
17. Describe the weathering process of hydrolysis.
a. Water is involved in chemical reactions that change minerals in a rock into new materials
18. Define migration.
a. Movement of dunes
19. List some features of glaciers.
a. Moraines, drumlins, kettle holes
20. Which particles are most easily moved by wind?
a. silt