Bedrock. Solid, unweathered rock that lies beneath regolith. Bedrock. Soil and Climate. Climate is most important factor influencing soil formation. Temperate climates. Temperatures range from cool to warm Rain fall is not excessive
-found in eastern United States
2. Pedocal – soil formed if rainfall is less then 65 cm a year (calcium carbonate)
-found in western United States
*rain always is washing away the A horizon but constant rotting vegetation covers the B Horizon
When soil is washed away by rainfall, furrows become larger forming gullies (gravity and water at work)
Sheet erosion is another type of soil erosion that strips away parallel layers of topsoil
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)
contour plowing: soil is plowed in circular bands that follow the shape of the land (prevents water from flowing directly down slope)
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.
Figure 21 Rockslide The scar on the side of this mountain in northwestern Wyoming was made by an enormous rockslide that happened more than 75years ago.The debris in the slide formed a dam 70 m high across the Gros Ventre River.
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
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
erosion of mountains: weathering and erosion wear down rugged peaks to rounded peaks and gentle slopes