Erosion

The process by which natural forces move weathered rock and soil from one place to another.

 The material moved by erosion is sediment. Sediment may consist of pieces of rock or soil or the remains of plants and animals.  Both weathering and erosion produce sediment.

Deposition Deposition occurs where the agents of erosion, deposit or lay down sediment. Deposition changes the shape of the land.

Shaping Earth’s Surface Weathering, erosion and deposition act together in a cycle that wears down and build’s up Earth’s surface. Erosion and deposition are at work everywhere on Earth. As a mountain wears down in one place, new landforms build up in other places. The cycle of erosion and deposition is never- ending.

 The erosion process occurs when water, ice, wind or gravity moves fragments of rock and soil.  The types of erosion are:  Water Erosion  Ice Erosion  Wind Erosion  Mass Movement

Water Erosion Runoff, rivers, streams

Runoff Moving water is the major agent of the erosion that has shaped Earth’s land surface. Erosion by water begins with the splash of rain. Some rainfall sinks into the ground. Some evaporates or is taken up by plants. As water moves over the land, it carries particles of sediment with it. This moving water is called runoff.

E ROSION BY R IVERS As the river flows from the mountains to the sea, the river forms a variety of features. Through erosion, a river creates valleys, waterfalls, flood plains, meanders, and oxbow lakes.

 As water moves it carries sediment with it. Any time moving water slows down, it deposits some of the sediment.  Deposition creates landforms such as alluvial fans and deltas. It can also add soil to the river’s flood plain.

Ice Erosion Glaciers

 Geologist define a glacier as any large mass of ice that moves slowly over land.  There are two kinds of glaciers- continental glaciers and valley glaciers.  A continental glacier covers much of the continent or large island.  A valley glacier is a long, narrow glacier that forms when snow and ice build up high in a mountain valley.

How Glaciers Shape the Land As a glacier flows over the land, it picks up rocks in a process called plucking. Beneath a glacier, the weight of the ice can break rocks apart. These rock fragments freeze to the bottom of the glacier. When the glacier moves it carries the rocks with it. Glacial Deposition occurs when a glacier melts, it deposits the sediment it eroded form the land, creating various landforms.

Wind Erosion

 Wind cause erosion by deflation and abrasion.  Deflation is the process by which wind picks up the smallest particles of sediment.  Abrasion by wind-carried sand can polish rocks, but causes little erosion.  Wind Erosion and Deposition may form sand dunes, and loess deposits.

 Gravity is the force that moves rock and other materials downhill. Gravity causes mass movement.  The different types of mass movement include landslides, mudflows, slump and creep.

Types of Mass Movement  Landslides- The most destructive type of mass movement which occurs when rock and soil slide quickly down a steep slope.  Mudflows- A mudflow is the rapid downhill movement of a mixture of water, rock and soil. Mudflows occur after heavy rains in a normally dry area and can contain as much as 60% of water.

 Slump- Occurs when a mass of rock and soil suddenly slips down a slope. Unlike a landslide, the material in a slump moves down in one large mass.  Creep- Is the very slow downhill movement of rock and soil. Creep often results from the freezing and thawing of water.

Mass Movements Landslides, mudslides, slump and creep landslide clip.mpeg