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Changing Earth’s surface. Weathering, Erosion, and Deposition & Mass Movement. Weathering. The chemical and physical processes that break down rock at Earth’s surface. . Chemical Weathering. The process that breaks down rocks through chemical changes. Examples of chemical weathering:
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Changing Earth’s surface Weathering, Erosion, and Deposition & Mass Movement
Weathering • The chemical and physical processes that break down rock at Earth’s surface.
Chemical Weathering • The process that breaks down rocks through chemical changes. • Examples of chemical weathering: • Acid rain • Acid from plants • Oxygen • Acid from lichens
Physical (Mechanical) Weathering • Process of breaking rocks apart without changing its chemical composition. • Examples: • Rapidly moving water • Ice wedging • Plant roots
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
Sediment • The material moved by erosion. • May consist of pieces of rock or soil or the remains of plants and animals
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
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.
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
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.
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.
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.
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.