Residual/Transported Soils, Erosion, and Erosion History

Parent Material Classified as either residual or transported Residual- soils that formed in their present location from the bedrock beneath Bedrock- The sold rock beneath the soil

Example: Sandstone Sandstone soils form from sandstone bedrock producing dry coarse soil. (mountain ridges)

Example: Limestone Limestone soils come from limestone bedrock producing soil good for farming. (Lancaster)

Transported Soils Soils that have been moved from their original location

Glacial Till Rocks and soils moved by glaciers

Aeolian Soil moved by wind

Colluvial Fallen rocks and soil along cliffs and slopes

Alluvial Soil moved by water (flooded stream banks)

What is Erosion? The movement of soil by wind or water to some new location. Naturally a slow process but speeds up quickly when it is exposed. Billions of tons of exposed topsoil are lost each year to erosion

Erosion History: Early Settlers The invention of the plow greatly increased the amount of erosion by exposing large areas of farmland Early colonists would grow one crop (monoculture) in the same place every year until the nutrients were used up and then they would move on leaving exposed soil behind.

Erosion History: Early Settlers Colonists moved west to the great plains where the soil was rich in organic matter.

Erosion History: Early 1900’s Farmland increased rapidly and by the 1930’s giant dust clouds of soil blew across the county due to dry exposed soil. (dust bowl) The government created the Soil conservation Service (SCS) (now the NRCS) within the Dept. of Agriculture to conserve the nation’s soils. The NRCS maps and surveys soil to plan methods of soil conservation.

Erosion History: Late 1900’s Modern technology has allowed the U.S. to increase its production allowing it to produce more food than needed. In the 70’s the U.S. started growing grains for other countries adding to the erosion problem (dust storms in CA.)

Erosion History: Today Many conservation practices are still ignored when using large machinery because many practices are more difficult to do on a large scale. Besides farming, highway construction, building construction, overgrazing and some logging activities all increase the rate of erosion

Types of Erosion: Rill Occurs on gentle slopes of exposed soil. Water creates small channels a few inches deep. It may turn into gully erosion on steeper slopes.

Types of Erosion: Gully Occurs on steep slopes. Fast moving water cuts deep ditches into the soil that can change the landscape.

Types of Erosion: Sheet Gradual removal of topsoil by wind or water. Occurs in thin layers on very gentle to non-sloping exposed soils. It can be seen by blowing dust and muddy water.

Types of Erosion: Mass Large movements of soil due to gravity. Several Types: Landslide Mudslide Rockfall Creep

Landslide

Mudslide

Rockfall

Creep

National Geographic Mudslide Video Induced Rockfall