Erosion - the process that moves weathered rock from one location to another
Depostion - the dropping of sediment
4 agents of erosion:
1. Gravity
2. Running Water
3. Glaciers
4. Wind
Gravity
Mass Movement - the sliding of a volume of loose material down a slope, caused by gravity
4 types:
1. Slump - a type of mass movement in which loose material slowly moves downhill a short distance, leaving a curved scar
2. Creep - a type of mass movement in which sediments move down a hill very slowly, sometimes causing posts to lean
3. Rockslides - large blocks of rock break loose from steep slopes and tumble quickly to the bottom
4. Mudflows - a thick mixture of water and sediments flowing downhill; normally occur in relatively dry areas; deposits are usually a cone-shaped mass
Running Water
- water erodes more sediments than any other agent of erosion due to its great energy of motion
Rill erosion - a type of erosion in which water swiftly running down a slope creates small channels in the soil; these channels can enlarge into gullies
Gully erosion - a type of erosion in which water swiftly running down a slope creates large channels in the soil or rock
Sheet erosion - a type of erosion in which water flowing over a gentle slope slowly removes sediment from the entire surface
Depostion by water
Alluvial fan - a deposit of sediment that occurs when water rushing down a slope abruptly slows at the bottom, depositing its sediment load
Delta - a triangular deposit of sediment that occurs when a stream or river slows as it empties into an ocean, gulf, or lake
Glaciers
Glacier - a moving mass of snow that has compacted into ice and is moving dowhill
Two types of glaciers :
Continental - a type of glacier in Earth's polar regions that cover a vast area; existing now only in Greenland and Antartica
Valley - the commonest type of glacier, occuring locally in mountain valleys where the average temperature allows snow to accumulate faster than it can melt
Plucking - a type of glacial erosion in which rock fragments from sand size to boulders are broken off and carried by the glacier
Till - a mixture of boulders, sand silt, and clay left by a melting glacier
Outwash - a glacial deposit left by streams flowing from a melting glacier
Wind
Deflation - erosion caused by wind as it wears away sediments such as clay, silt and sand
Abrasion - a type of erosion caused when windblown or waterborne sand grains strike other sand grains and rocks, breaking off small fragments
Loess - a thick deposit of very fine, wind-eroded sediments
Dunes - the most common of wind deposits; consist mainly of sand
Developing land prone to erosion
Three preventative measures:
Terraces - broad steplike cuts in the side of a slope; the energy of motion of water is reduced as it flows over the terrace
Vegetation - roots help to hold soil together
Retaining walls - reinforced concrete helps to hold back soil