Erosion

Various forces move weathered fragments of rock away from where the weathering

erosion is the process by which the products of weathering are transported agents of erosion are gravity, wind, glaciers, water, ocean waves, currents streams, groundwater

Soil Erosion occurs world wide and is normally a slow process ordinarily, new residual soil forms about as fast as the existing soil erodes However, unwise use of the land and unusual climatic conditions can upset this natural balance

Accelerated Soil Erosion unwise farming and ranching methods increase soil erosion one example is clearing of trees,small plants, and animal overgrazing another example is furrows plowed in land

Gullying is when soil is washed away by rainfall becomes larger forming gullies (gravity and water at work)

Sheet erosion is another type of soil erosion that strips away parallel layers of topsoil may occur when continuous rainfall evenly washes away the topsoil can also be caused by wind during unusually dry periods

Severe soil erosion from wind in the 1930's was a result of drought coupled with unsound farming practices.

The photo on the right though, was taken at 10:00 AM, March 13, 1991 in downtown Topeka, Kansas, looking into the sun. There was so much soil in the air it darkened the sky. So the problem is not just something of the past.

constant erosion reduces the fertility of the soil by removing the A horizon, which is rich in humus (unable to grow crops)

Soil Conservation contour plowing: soil is plowed in circular bands that follow the shape of the land (prevents water from flowing directly down slope)

strip cropping: crops are planted in alternate bands

Contour cropping of corn, alfalfa and wheat.

Contour farming (planting crops along the slope of the land) and contour strip cropping (alternating different crops in the same field) reduces soil erosion. Traps soil on the field.

terracing: construction of step-like ridges that follow the contours of a sloped field

During heavy rain storms terraces catch water and lead it slowly off the field. Slowing down the speed of flowing water reduces soil erosion.

crop rotation: farmers plant one type of crop one year and a different type of crop the next year

                                                    <> With the development site cleared of all vegetation, area is now prone to soil losses in excess of 70 tons per acre.

Gravity and Erosion Gravity, through its downward pull, causes rock fragments to move down inclines mass movement is the movement of fragments down a slope (rapid or slow)

talus: a pile of rock fragments that accumulates at the base of the slope in piles

rockfall: the fall of rock from a steep cliff is the most rapid Rapid mass movements rockfall: the fall of rock from a steep cliff is the most rapid can be from tiny fragments to large boulders

landslide: sudden movement of masses of loose rock and soil down the slope of a hill

Hinsdale County, Colorado 700 years old and still moving Slumgullion landslide Hinsdale County, Colorado 700 years old and still moving

mudflow: the rapid movement of a large mass of mud

slump: downhill movement of a large block of soil under the influence of gravity

A slump is a type of slope failure which involves the rotational movement of soil or rock

Slow mass movements solifluction “slow flow” : slow downslope flow of wet, muddy topsoil over frozen or clay-rich subsoil

creep: extremely slow downhill movement of weathered rock material