Erosion In Depth

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.

Erosion is the process that breaks things down. As far as we're concerned, erosion is the breakdown of the continents and the land around you. The overall effect of breaking down and weathering the land is called denudation. Denudation is the process of erosion. In nature, large things are broken down into smaller things. Boulders become sand. Mountains are rained on and become hills. The pieces of the mountain become smaller pieces and go down the sides of hills. Weathering and erosion always happen in a downhill direction. Erosion is an easy idea to understand. If you see a rock, pull it out of a mountain. Then throw it down on the ground. You are now a part of the erosion of that mountain. You have taken a big object (a mountain) and started to make little objects out of it (a rock). When that rock hit the ground, it could have cracked and made some tiny pieces of rock (sand). Erosion is just that easy. When it rains, the same process happens. Rocks are washed down a mountain or down a stream. Soils are washed away. The ocean beats against a cliff and breaks it apart. They are all examples of denudation.

Things don't just disappear. The masses of dirt and rock are moved to another form and place. Scientists call it mass wasting. The wasting is the loss of matter in one place. Mass wasting can happen two ways: 1) mechanical, similar to breaking a rock with a hammer; and 2) chemical, similar to pouring acid on a rock to dissolve it.

DOES EROSION BUILD THINGS UP?Erosion happens at the tops of mountains and under the soil. Water and chemicals get into the rocks and break them up through those mechanical and chemical forces. Erosion in one area can actually build up lower areas. Think about a mountain range and a river. As the mountain erodes, the river carries sediment downstream towards the ocean. That sediment slowly builds up and creates new wetlands at the mouth of the river. The swamps of Louisiana are good examples of sediment carried by the Mississippi River and collected at the

Reference:"Erosion." Geography 4 Kids. 26 May 2008 .