Transcript u2 w1 d2 pres - Cobb Learning

Erosion
Deposition
Agents, Forces, and Results
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below_Hay_Bluff_-_geograph.org.uk_-_1074175.jpg
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Seminole_Canyon.JPG
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Erosion
•Erosion – moving of rock and other materials from
one place to a new location
–Three processes must take place:
• detachment of particles (weathering)
• lifting them
• transporting them
–Agents of erosion:
• flowing water
• moving ice
• waves
• gravity
• wind
• animal activity
Erosion
•Wind – wears away rocks and is responsible for the
creation of deserts such as the Sahara and the Gobi
- It is most effective when moving loose, light weight materials
– Main effects:
1. Wind lifts small particles and moves them away.
2. Suspended particles may cause weathering on solid objects by abrasion
(rubbing).
– Usually occurs in areas where there is not enough rainfall to support vegetation
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res_in_Wadi_Al-Hitan.jpg
Erosion
•Water – most influential force in weathering and erosion
–Moves materials
–Transports large objects with fast moving streams and
powerful waves
–Wears away (weathers) rocks and other materials.
• rivers
• lakes
• oceans
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rosion_below_Scarsoch_Bheag__geograph.org.uk_-_1367808.jpg
Erosion
• Waves – relentless pounding
• Erodes:
• softer/weaker rock breakdown (weather) first
• harder/more resistant materials are left behind
• Can take over 100 years to weather a rock to sand which is
then carried to a new location by the water
• Energy of waves and chemicals contained in the water
weather and erode the rock off the coastline.
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ck_Head_-_geograph.org.uk_-_369272.jpg
Erosion
•Mass 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
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ry_-_geograph.org.uk_-_1711962.jpg
Erosion
• Ice – 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
• striations (grooves) left in rock
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Deposition
•Deposition – 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.
Deposition
Wind speed can be related to variations in heating
and cooling.
 Transportation of particles in wind:
– Fine particles in suspension can be hundreds of km from its original
source
– 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
Deposition
• Running water enters a large, fairly still body of water
and 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
Deposition
• Glacial 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
• WEATHERING – Think of weather wearing rock down.
• EROSION – Think of a road and traveling.
• DEPOSITION – Think of depositing money into a bank.