Erosion and Deposition

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


Notes

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