Forces That Shape Our Earth:

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Forces That Shape Our Earth

• UNIT 3
• Weathering
• And
• Erosion

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Weathering Erosion

• Erosion and weathering are major forces that
  shape Earths surface.
• For example, the Grand Canyon was formed through
  erosion by the Colorado River running through it!
  

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What is weathering?

• Weathering The breaking down of rocks into
  smaller pieces.
• 1. Mechanical /Physical
• 2. Chemical

Hulk Rock Smash!
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So what is erosion?

• Erosion
• The movement
• of weathered
• rock by wind, water, glaciers gravity

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Types of Weathering

• Mechanical/Physical
• Rock is physically broken into smaller pieces
  (larger pieces become smaller pieces of the same
  rock)
• Chemical
• Rock is chemically changed (like rusting or
  dissolving away)

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5 Agents of Mechanical Weathering

1. Release of Pressure
2. Freezing Thawing
3. Animal Actions
4. Plant Growth
5. Abrasion

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Release of Pressure

• As the surface of a rock is eroded, the rock
  begins to release pressure
• Causes top layers of the rock to crack and flake
  off

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Release of pressure rock cracks like an egg shell
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Freezing Thawing

• When water in the cracks of rocks freezes it
  expands causing the crack to enlarge or get
  bigger. The ice melts refreezes over over,
  breaking the rock apart.

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Result of Freezing Thawing
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Animal Actions

• Animals dig (burrow) through the ground to make
  their homes. This loosens the soil breaks apart
  rocks.

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Plant Root Growth

• Plants roots can grow into cracks in the rock,
  slowly breaking them apart.

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Abrasion

• Sand and other rock particles in wind, water or
  ice can wear away exposed rock surfaces.
• Like sandblasting or sandpaper on wood

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5 Agents of Chemical Weathering

• Water
• Oxygen
• Carbon Dioxide
• Living Organisms
• Acid Rain

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Water

• Water dissolves rock
• Water is the most important cause of chemical
  weathering

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Oxygen

• Oxygen Water Iron Rust through the Chemical
  reaction called Oxidation
• Rock will become crumbly, soft, and appear
  reddish-brown in color

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Rusted rock on hillside
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Carbon Dioxide

• CO2 rainwater Carbonic Acid
• Carbonic Acid weathers softer rock like limestone
  marble as it seeps into spaces in rock.
• Ex sinkholes, caves

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Living Organisms

• The roots of plants make a weak acid that slowly
  dissolves rocks around the plant.

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Lichens grow on rock
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Acid Rain

• Acid rain causes rocks to weather very rapidly.

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