1. Erosion and Deposition

2. What Caused This?

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

4. What Is Wind Erosion?
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:
Wind lifts small particles and moves them away.
Suspended particles may cause erosion on solid objects by abrasion (rubbing).
Occurs in areas where there is not enough rainfall to support vegetation

5. What Is Water Erosion? Water – most influential force in erosion
Moves materials
Transports large objects with fast moving streams
Wears away rocks:
rivers
lakes
oceans
Ground/sinkholes

9. What Is Wave 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 chemicals contained in the water erode the rock off the coastline.

10. What Is Gravitational 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

11. What Is Glacial 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

13. What is 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.

14. Deposition - Wind
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.

15. Deposition - Water
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.

17. Deposition - Ice
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.

18. What’s the Difference?
WEATHERING – Think of weather wearing rock down.
EROSION – Think of a road and traveling.
DEPOSITION – Think of depositing money into a bank.

19. Running Water Deposits Well-Sorted Particles
Vertical Sorting – When sediments are suddenly deposited into water. The particles separate by size with the largest on the bottom and smallest on top.

20. Horizontal Sorting – When rivers empty their sediments into quiet bodies of water. Particles are sorted by size with larger particles being found closer to the shore and smaller particles being carried out into the body of water to be deposited.
Delta – A fan-shaped deposit of sediment at the mouth of a river