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Erosion and Deposition


Erosion and Deposition Agents, Forces, and Results What Caused This? What is Erosion? Erosion - moving of rock material (sediment) from one place to a new location ... – PowerPoint PPT presentation

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Title: Erosion and Deposition

Erosion and Deposition
  • Agents, Forces, and Results

What Caused This?
What is Erosion?
  • Erosion - moving of rock material (sediment) from
    one place to a new location
  • For erosion to occur three processes must take
    place detachment of particles, lifting them, and
    transporting them
  • Many agents of erosion - flowing water, moving
    ice, waves, gravity, or wind
  • Sand consists of small pieces of rock that have
    been weathered from a parent rock, eroded, and
    deposited somewhere else

What Is Wind Erosion?
  • Wind - responsible for wearing away rocks and
    creating great deserts like the Sahara Desert and
  • Most effective in moving loose material
  • Two 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

What Is Water Erosion?
  • Water - most influential force in erosion
  • Ability to move materials from one location to
    another over long distances
  • The faster water moves in streams the larger
    objects it can pick up and transport
  • Responsible for wearing away of rocks in rivers,
    lakes, and the oceans

What Is Wave Erosion?
  • Waves - relentless pounding
  • Erodes the softer, weaker parts of the rock
    first, leaving harder, more resistant rock behind
  • Can take over 100 years to erode a rock to sand
  • Energy of waves along with the chemical content
    of the water erodes the rock off the coastline

What Is Gravitational Erosion?
  • Mass movement - downward movement of rock and
    sediments, mainly due to the force of gravity.
  • Moves material from higher elevations to lower
    elevations where streams and glaciers can pick up
    the material and move it to lower elevations
  • Process is occurring continuously on all slopes,
    some act very slowly while others occur very
    suddenly until equilibrium is reached

What Is Glacial Erosion?
  • Ice - moves and carries rocks, grinding the rocks
    beneath the glacier
  • Glaciers pluck and abrade to cause erosion
  • Plucking occurs when water enters cracks under
    the glacier, freezing, and breaking off pieces of
    rock that are then carried by the glacier.
  • Abrasion cuts into the rock under the glacier,
    smoothing and polishing the rock surface

What is Deposition?
  • Deposition - laying down of sediment that has
    been transported by something 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. This settling is deposition.
  • If the 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
  • Wind speed can be related to variations in
    heating and cooling
  • Wind can transport fine particles in suspension
    hundreds of km from its original source in the
  • Heavier material may be blown along the ground.
  • Material is eventually deposited when the wind
    changes direction or loses its strength.
  • Obstacles, whether natural of man-made, will
    often decide where the deposition occurs and the
    nature of the feature formed.

Deposition - Water
  • Running water enters a large, fairly still body
    of water and its speed decreases.
  • As speed decreases, water's ability to carry
    sediments decreases
  • Sediments carried by running water are deposited
    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
  • Occurs in streams, rivers, oceans, etc.

Deposition - Ice
  • Glacial flows of ice - become slower when the ice
    begins melting
  • Deposits left by glaciers are called moraines
  • outwashes
  • Moraines are large chunks of broken rock left
    at the base
  • and sides of the glacier as it melts and
  • Finer material is carried in the rivers that form
    when the glacial ice melts. The deposits of these
    rivers look similar to normal river deposits and
    are called outwashes

Whats the Difference?
  • WEATHERING - think weather wearing rock down
  • EROSION - think of a road and traveling
  • DEPOSITION think of depositing money in a bank
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