2. Chapters 4 & 5 Weathering and Erosion

3. Weathering Weathering is the breaking down of rocks and other materials 2 types of weathering –Mechanical –Chemical

4. Mechanical/Physical Weathering Mechanical Weathering occurs when rocks are broken down into smaller pieces, but the chemical composition is not changed Examples: temperature, frost, tree roots, gravity (abrasion)

5. Physical Weathering

6. Mechanical Weathering Temperature - rocks expand when they are heated up, and contract when they are cooled. This process breaks rock. Frost Action- water gets into cracks of rock and freezes when it gets cold. Crack expands Organic Activity - roots of trees break rocks Gravity - rocks are pulled downward by gravity Abrasion - wind blown sand wears away rocks (also water running over rocks)

7. Chemical Weathering Chemical weathering occurs when rocks are broken down and their chemical composition is changed Examples: water, carbon dioxide, oxygen, plants

8. Chemical Weathering

9. Water - most chemical weathering occurs w/ water/CO 2. Water dissolves minerals. Oxidation - process in which oxygen chemically combines with another substance. (iron in rocks can rust) Carbonation - occurs when CO 2 dissolves in water and forms carbonic acid. Plant Acids - moss and lichens produce weak acids that dissolve minerals in rocks

10. Soil Formation Soil is formed when rocks are continuously broken down by weathering. Soil that stay close is called residual, soil that is moved is called transported. Bedrock is the layer of rock beneath the soil

11. Erosion Erosion is the process by which weathered rock is moved. Grand Canyon was formed by erosion. Causes of erosion: gravity, wind, running water, glaciers, and waves. Deposition is the process by which sediments are laid down in a new place.

12. Erosion

13. Gravity pulls rocks and soil down slopes. Examples: landslide or mudflow Wind is most active agent of erosion in deserts and on beaches. Wind erosion can form dunes or caves. Running water is the major cause of erosion. Examples: rivers, streams, and runoff. Glaciers ice erodes rocks beneath it by abrasion. Waves erode and shape shorelines.

14. Erosion Caused by Wind

15. Humans Impact Erosion