Chapter 8

EROSION & DEPOSITION

Chapter 8 Section 1

CHANGING EARTH’S SURFACE

WEARING DOWN AND BUILDING UP

Erosion- the process by which natural forces move weathered rock and soil from one place to another

Example- landslide, gravity, running water, glaciers, waves, wind

Sediment- material moved by erosion

Deposition- occurs where the agents of erosion lay down sediment; changes the shape of the land

Weathering, erosion, and deposition act together in a cycle that wears down and builds up Earth’s surface

WHAT HAPPENS TO SEDIMENT AS A RESULT OF EROSION AND DEPOSITION?

Erosion moves sediment from one place to another. Deposition lays down sediment in new locations, building new landforms.

MASS MOVEMENT

Gravity

Gravity is the force that moves rock and other materials downhill

Gravity causes mass movement, any one of several process that move sediment downhill

Mass movement includes landslides, mudslides, slump, and creep

Landslides

Landslides are the most destructive kind of mass movement

Occurs when rock and soil slide quickly down a steep slope

MASS MOVEMENT

Mudflows Mudflows are rapid

downhill movement of a mixture of water, rock, and soil

Mudflows often occur after heavy rains in a normally dry area

Often occurs in areas with clay soils

Slump

Slump occurs when a mass of rock and soil suddenly slips down a slope

The material in slump moves down in one large mass

Occurs when water soaks the base of a mass of soil that is rich in clay

CREEP

Creep is the very slow downhill movement of rock and soil

Creep occurs so slowly, you hardly notice it

Creep may tilt objects at spooky angles

Creep results from freezing and thawing of water in cracked layers of rock beneath the soil

REVIEW

Explain the difference between erosion and deposition.

Erosion moves sediment from one place to another, while deposition lays down sediment in new locations

What force causes erosion?

The force of gravity and the forces exerted by running water, glaciers, waves, and wind cause erosion

What are four types of mass movement?

Landslides, mudflows, slump, and creep

Why would a landslide be more likely on a steep mountain than on a gently sloping hill?

On a gently sloping hill, the force of gravity cannot pull down rock and soil quickly because of the friction between the hill and the rock and soil. On a steep mountain, though, the force of gravity can much more easily overcome the force of friction