Erosional Forces

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Erosional Forces
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Erosional Forces

• Gravity
• Glaciers
• Wind
• Water

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Erosional Forces

• These agents of erosion can only move material
  when they have enough energy to move the object.
• Another thing they have in common is they will
  deposit, or drop, the material they carry when
  they have lost the energy.

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Gravity as a force

• Gravity is the force which Earth has on all
  objects.
• It pulls boulders, soil and everything else to
  the lowest point possible.
• When gravity moves materials downslope this is
  then called mass movement.

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Some mass movements are slow
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Some mass movements are fast
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Erosion by slump

• Slump is when soil or rock move as one piece down
  a slope as one large mass.

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Erosion by Slump
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Erosion by creep

• Creep is the slow movement of soil downslope that
  causes fence poles, telephone poles to tilt in
  the direction of movement.

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Erosion by rock slides

• Rock slides happen when hudge blocks of rock
  break loose and tumble downslope.
• Rock slides can be very fast and very dangerous
• Very common in mountainous areas.

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Erosion by Rock Slides
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Glaciers as agents of erosion.

• A moving mass of ice and snow is called a
  glacier.
• Glaciers form when snow and ice build up faster
  than they melt.
• There are two types of glaciers
• Continental glaciers and
• Valley glaciers

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Continental Glaciers

• Continental glaciers cover large parts of
  continents such as Antarctica.

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Glacier Erratic
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Glaciers

• About 20,000 years ago glaciers covered 28 of
  the Earths surface.
• Since that time they have been melting and now
  cover about 10 of the Earth.
• Greenland and Antarctica are almost completely
  covered in ice.

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Glacier Erosion

• Glacial plucking is when large boulders are
  removed from the sides of valley and picked up by
  the glacier.

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Glacial plucking of rocks
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Valley Glaciers
Mountain Horns
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Valley Glacier Features

• Valleys that show evidence of glaciers are U
  shaped.
• Yosemite Valley is just such an example.

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Half Dome
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Wind Erosion

• Wind is a very powerful force in erosion.
• Through blowing away silt and clay by deflation
  or by eroding down rocks by abrasion.

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Wind Erosion
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Deflation or blowing away of other material by
wind.
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Wind erosion by abrasion or eroding away other
material.
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The End