CHANGING EARTH’S SURFACEWeathering, 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.

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.