Erosion and Deposition PPT
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Transcript Erosion and Deposition PPT
Erosion
Deposition
Agents, Forces, and Results
http://commons.wikimedia.org/wiki/File:Water_erosion_
below_Hay_Bluff_-_geograph.org.uk_-_1074175.jpg
http://commons.wikimedia.org/wiki/File:Wind_erosion_
Seminole_Canyon.JPG
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ntian_Clay_Beds_-_geograph.org.uk__1776748.jpg
Erosion
•Erosion – moving of rock material from one place
to a new location
– Three processes must take place:
• detachment of particles
• lifting them
• transporting them
– Agents of erosion:
• flowing water
• moving ice
• waves
• gravity
• wind
– Sand consists of small pieces of rock that have been:
• weathered from a parent rock
• eroded
• deposited somewhere else
Erosion
•Wind – responsible for wearing away rocks and
creating great deserts like the Sahara Desert and Gobi
– Most effective in moving loose material
– Main effects:
1. Wind causes small particles to be lifted and moved away.
2. Suspended particles may impact on solid objects causing erosion by
abrasion (rubbing).
– Occurs in areas where there is not enough rainfall to support vegetation
http://commons.wikimedia.org/wiki/File:Wind_Erosion_Featu
res_in_Wadi_Al-Hitan.jpg
Erosion
•Water – 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_e
rosion_below_Scarsoch_Bheag__geograph.org.uk_-_1367808.jpg
Erosion
•Waves – 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 chemical content of the water erodes
the rock off the coastline.
http://commons.wikimedia.org/wiki/File:Wave_Erosion,_Downpatri
ck_Head_-_geograph.org.uk_-_369272.jpg
Erosion
•Mass movement – downward movement of rock
and sediments, mainly due 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
http://commons.wikimedia.org/wiki/File:Ushaped_valley_at_the_head_of_Leh_valley,_Ladakh_(2).JPG
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 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
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:
– The deposits of these rivers look similar to normal river deposits and are
called outwashes.
– Moraines are large chunks of broken rock left at the base and sides of the
glacier as it melts and recedes.
– Finer material is carried in the rivers that form when the glacial ice melts.
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.