Weathering and Erosion

Mayble Thu Nov 13, 2008 11:39 am

What is Erosion?

What causes valleys to form? Why do streams and lakes get muddy after a rain storm? Why are the rocks at the bottom of a river usually round? The answer to all these questions is EROSION!
Erosion is the process by which the surface of the Earth gets worn down. Erosion can be caused by natural elements such as wind and glacial ice. But anyone who has ever seen a picture of the Grand Canyon knows that nothing beats the slow steady movement of water when it comes to changing the Earth.
The key to erosion is something called "fluid flow."Water, air, and even ice are fluids because they tend to flow from one place to another due to the force of gravity. Of the three, liquid water is the most common agent of erosion because there's so much of it on the surface of the Earth.

What is Weathering?

Weathering is the natural decaying or wasting of rocks, soils and their minerals at or near the surface of the earth. Weathering breaks down and loosens the surface minerals of rock so they can be transported away by agents of erosion such as water, wind and ice. It eventually converts the rocks into sand, clay, and dissolved salts. All soil is derived from weathered materials, a soil weathered from a mix of different rock types often makes a more fertile soil.

The rate at which weathering occurs depends a great deal on the climate, an exposed big stone in a desert typically show little chemical weathering, whereas exposed big stones in a rain forest are often so weathered that they will crumble under a single blow.