Agents, Forces, and ResultsAgents, Forces, and Results

http://commons.wikimedia.org/wiki/File:Wind_erosion_Seminole_Canyon.JPG

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•WindWind – wears away rocks and is responsible for the creation of deserts such as the Sahara and the Gobi

- Most effective in moving loose material – Main effects:

1. Wind lifts small particles and moves them away. 2. Suspended particles may cause erosion on solid objects by abrasion

(rubbing).– Occurs in areas where there is not enough rainfall to support vegetation

http://commons.wikimedia.org/wiki/File:Wind_Erosion_Features_in_Wadi_Al-Hitan.jpg

•WaterWater – most influential force in erosion–Moves materials –Transports large objects with fast moving streams–Wears away rocks:• rivers• lakes• oceans

http://commons.wikimedia.org/wiki/File:Water_erosion_below_Scarsoch_Bheag_-_geograph.org.uk_-_1367808.jpg

• WavesWaves – relentless pounding • Erodes:• softer/weaker rock first• harder/more resistant left behind

• Can take over 100 years to erode a rock to sand • Energy of waves and chemicals contained in the water erode

the rock off the coastline.

http://commons.wikimedia.org/wiki/File:Wave_Erosion,_Downpatrick_Head_-_geograph.org.uk_-_369272.jpg

•Mass MovementMass Movement – downward movement of rock and sediments, due primarily to the force of gravity –Streams and glaciers• move material from higher to lower elevation–Occurs continuously on all slopes» slow moving and sudden movement until equilibrium is reached

http://commons.wikimedia.org/wiki/File:Purbeck_,_Old_Harry_-_geograph.org.uk_-_1711962.jpg

• IceIce – moves and carries rocks, grinding the rocks beneath the glacier– Plucking occurs when water enters cracks under the glacier.• freezing• breaking off pieces of rock that are then carried by the glacier

–Abrade (abrasion)• cuts into the rock under the glacier• smoothing • polishing the rock surface

http://commons.wikimedia.org/wiki/File:U-shaped_valley_at_the_head_of_Leh_valley,_Ladakh_(2).JPG

•DepositionDeposition – laying down of sediment that has been transported by a medium such as wind, water, or ice –Process of erosion stops:• when the moving particles fall out of the transporting

medium and settle on a surface–Speed of the medium slows or the resistance of the particles

increases, the balance changes and causes deposition–Speed can be reduced by large rocks, hills, vegetation, etc.

Wind speed can be related to variations in heating Wind speed can be related to variations in heating and cooling.and cooling.Transportation of particles in wind:– Fine particles in suspension hundreds of km from its original source in

the desert–Heavier material may be blown along the ground.–Material is deposited when the wind changes direction or loses its

strength.

http://commons.wikimedia.org/wiki/File:Desert_Chihuahuan_Big_Bend.JPG

• Running water enters a large, fairly still body of water Running water enters a large, fairly still body of water and its speed decreasesand its speed decreases• SPEED• As the speed of the water decreases, the water's ability to carry

sediment also decreases.• Deposited in streams, rivers, and oceans:• Running water deposits sediments where the slowing water can no

longer move them.• Largest particles are deposited near the shore. • Increasingly smaller particles settle out farther from the shore where

the water is calmer.

http://commons.wikimedia.org/wiki/File:Enchanted_Rock,_stream.jpg

• Glacial flows of iceGlacial flows of ice – become slower when the ice begins melting

– Deposits left by glaciers:–Outwashes are deposits similar to those left by rivers.– Large chunks of broken rock deposited at the base and sides of the glacier as

it melts and recedes are called Moraines.–When the glacial ice melts, smaller material is carried by the rivers.

http://commons.wikimedia.org/wiki/File:Cavell_Glacier_with_Crevices_and_Annual_Rings.jpg

• WEATHERINGWEATHERING – Think of weather wearing rock down.

• EROSIONEROSION – Think of a road and traveling.

• DEPOSITIONDEPOSITION – Think of depositing money into a bank.