1. CHANGING EARTH’S SURFACE Weathering, Erosion, and Deposition & Mass Movement

2. Weathering  The chemical and physical processes that break down rock at Earth’s surface.

3. Chemical Weathering  The process that breaks down rocks through chemical changes.  Examples of chemical weathering:  Acid rain  Acid from plants  Oxygen  Acid from lichens

4. Physical (Mechanical) Weathering  Process of breaking rocks apart without changing its chemical composition.  Examples:  Rapidly moving water  Ice wedging  Plant roots

5. What is erosion?  Erosion is the process by which natural forces move weathered rock and soil from one place to another.  Agents of Erosion:  Gravity  Running Water  Glaciers  Waves  Wind

6. Sediment  The material moved by erosion.  May consist of pieces of rock or soil or the remains of plants and animals

7. Deposition  Occurs where the agents of erosion deposit, or lay down, sediment.  Changes the shape of the land.  Examples:  Alluvial fans  Flood plains  Deltas  Beaches

8. Geologic Cycle  Weathering, erosion, and deposition act together in a cycle that wears down and builds up Earth’s surface. This cycle is called the geologic cycle.

9. Geologic Cycle

10. Gravitational Erosion (Mass Movement)  Gravity is the force that moves rock and other materials downhill.  Gravity causes mass movement.  Mass movement can be rapid or slow.  Examples:  Landslides  Mudflows  Slump  Creep

11. Landslides  A mass movement that occurs when rock and soil slide rapidly down a steep slope.  Contain huge masses of rock or only a small amount of rock and soil.  Can be triggered by earthquakes.

12. Mudflows  A rapid downhill movement of a mixture of water, rock, and soil. Amount of water can be as high as 60%.  Often occur after heavy rains in a normally dry area.  Can be triggered by earthquakes.

13. Slump  A type of mass movement in which a mass of rock and soil rapidly slips down a slope.  The material moves in one large mass.  Often occurs when water soaks the bottom of soil that is rich in clay.

14. Creep  The very slow downhill movement of rock and soil.  Can even occur on gentle slopes.  Often result from the freezing and thawing of water in cracked layers of rock beneath the soil.  Change can occur so slow that it is hard to detect.