EROSION

Erosion can occur quickly or slowly. Erosion is the process by which natural forces move weathered rock and soil from one place to another. Erosion can occur quickly or slowly.

Erosion occurs because of the actions of gravity, ice, wind, and water.

GRAVITY

When gravity alone causes rock or sediment to move down a slope, the erosion is called mass movement.

4 Types of Mass Movement Creep – Sediments move downhill very slowly. Slump – Rock or sediment moves suddenly downhill in one large mass. Rockslides & Landslides – Layers of rock or land break loose and slide quickly downhill. Mudflows – A mass of wet sediment flows rapidly downhill.

GLACIERS

When glaciers get thick enough, gravity causes them to flow downhill When glaciers get thick enough, gravity causes them to flow downhill. As they move, they erode materials from some areas and deposit sediment in other areas.

2 Types of Glaciers Continental Glaciers spread out in all directions. They cover much of a continent or large island. (ex: Antarctica and Greenland) Valley Glaciers move down valleys that have already been cut by rivers. They are much smaller but can still be tens of kilometers long.

Glaciers cause erosion by two processes: As a glacier flows over land, it picks up rocks. This process is called plucking. When the glacier moves, it carries the rocks with it. Many rocks remain on the bottom of the glacier and get dragged across the land, making scratches and gouges. This process is called abrasion.

New landforms can be developed when glaciers melt and deposit the sediment they have been carrying.

WIND

Wind by itself is the weakest agent of erosion. It can still be a powerful force in shaping the land in areas where there are few plants to hold the soil in place.

Wind blows small, loose sediment from Earth’s surface, but often leaves behind particles that are too heavy to move. This process is called deflation.

When sediments are blown by strong winds, abrasion can make pits in rocks and produce smooth, polished surfaces.

When wind blows around an obstacle, it slows down When wind blows around an obstacle, it slows down. This causes sand that is carried by the wind to be deposited, sometimes forming sand dunes.

WATER

Water is a major agent of erosion. Streams are the most important agent of erosion on Earth!

Water that flows over Earth’s surface is called runoff. This water carries loose sediment with it causing erosion. The more speed water has, the more material it can carry with it.

As runoff travels, it forms tiny grooves in the soil called rills. As many rills flow into one another, they grow larger, forming gullies. As many gullies join together, they form streams, which can eventually grow larger and form rivers.

Anytime moving water slows down, such as when rivers enter oceans or lakes, sediment is deposited. This can create landforms such as sand bars and deltas. This is known as deposition.

When rain falls or snow melts, not all of the water evaporates or becomes runoff. Some water soaks into the ground. This groundwater can cause erosion, forming caves and making stalactites and stalagmites.

Acting like drills or buzz saws, waves erode the solid rock of the coast into cliffs and caves. Large waves can hit rocks along the shore with great force, eventually causing pieces of rock to break off. Waves also cause the sediment they carry to wear away rock through abrasion.

Waves also deposit sediment they are carrying, forming features such as beaches.

EROSION CAN BE BEAUTIFUL!