Earth Geology Erosion

Erosion 

The word "erosion" comes from an old word meaning "eat away." You see erosion happening where the forces of nature move soil and rock. These agents of erosion are water, wind, ice and gravity. Living things, like plants, animals, and even tiny bacteria also do their part. Its surface features -- everything we see on the earth's surface -- have been shaped by the forces of nature over very long periods of time.

Running water is by far the most important agent of erosion within our watershed. The surface features of the watershed come directly from the action of running water, both on the surface and also underground. Gravity is the force that causes water to run downhill and erode the slopes. It is also causes erosion by causing rock falls and landslides. Burrowing things, hoofed animals, plant roots and humans are perhaps the most important agents of erosion among living things. 

An especially important part of erosion is weathering. Weathering is chemical and physical breaking down of rocks and earth materials. Weathering is the main thing producing soil, and it comes before or goes along with almost all erosion. 

The Atlas talks about erosion in two sections: field and slope erosion and valley and stream erosion. These are much the same, but valley and stream erosion takes much longer. We can see field and slope erosion while it happens, washing soil off the fields of the hill farmer. Stream and valley erosion, works over hundreds, thousands, and millions of years. It has made the shape of Bryant Creek and its tributaries what we see today.