erosion and deposition

1. Agents, Forces, and Results
Erosion
Deposition

2. http://commons.wikimedia.org/wiki/File:Wind_erosion_
Seminole_Canyon.JPG
http://commons.wikimedia.org/wiki/File:Bave
ntian_Clay_Beds_-_geograph.org.uk_-
_1776748.jpg
http://commons.wikimedia.org/wiki/File:Water_erosion_
below_Hay_Bluff_-_geograph.org.uk_-_1074175.jpg

3. •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 is composed of small pieces of rock that have been:
• weathered from a parent rock
• eroded
• deposited somewhere else
Erosion

4. •Wind – 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
Erosion
http://commons.wikimedia.org/wiki/File:Wind_Erosion_Featu
res_in_Wadi_Al-Hitan.jpg

5. •Water– most influential force in erosion
–Moves materials
–Transports large objects with fast moving streams
–Wears away rocks:
• rivers
• lakes
• oceans
Erosion
http://commons.wikimedia.org/wiki/File:Water_e
rosion_below_Scarsoch_Bheag_-
_geograph.org.uk_-_1367808.jpg

6. • 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 chemicals contained in the water erode
the rock off the coastline.
Erosion
http://commons.wikimedia.org/wiki/File:Wave_Erosion,_Downpatri
ck_Head_-_geograph.org.uk_-_369272.jpg

7. •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
Erosion
http://commons.wikimedia.org/wiki/File:Purbeck_,_Old_Har
ry_-_geograph.org.uk_-_1711962.jpg

8. • 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
Erosion
http://commons.wikimedia.org/wiki/File:U-
shaped_valley_at_the_head_of_Leh_valley,_Ladakh_(2).JPG

9. •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

10. 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.
Deposition
http://commons.wikimedia.org/wiki/File:Desert_Chihuahuan_Big_Bend.JPG

11. • 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.
Deposition
http://commons.wikimedia.org/wiki/File:Enchanted_Rock,_stream.jpg

12. • 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.
Deposition
http://commons.wikimedia.org/wiki/File:Cavell_Glacier_with_Crevices_and_Annual_Rings.jpg

13. • WEATHERING – Think of weather wearing rock down.
• EROSION – Think of a road and traveling.
• DEPOSITION – Think of depositing money into a bank.