Earth Notes

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Earth Notes






Chapter 2 Section 2

• Forces of Change

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The Earths Interior

• Inner Core about 4,000 miles below the surface
  of the Earth
• Outer Core 1,400 miles thick, temperature
  reaches 8500F

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Earths Interior (cont)

• Mantle layer of hot, dense rock MAGMA

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Earths Interior (cont)

• Crust rocky shell forming Earths surface.
• The crust is broken into slabs of rock called
  plates.
• Natural forces interact with the crust, creating
  landforms on the surface of the earth.
• Below the oceans, the crust is about 5 miles
  thick. Below the continents it averages 22 miles
  in thickness.

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Earths Interior (cont)

• Plates - float on a melted layer in the upper
  mantle
• - carry the earths oceans and continents

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Internal Forces of Change
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The Plate Tectonic Theory

• The lithosphere the earths crust and upper
  layer of the mantle is broken into a number of
  large, moving plates.

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The Plate Tectonic Theory

• The plates slide very slowly over a hot, pliable
  layer of mantle.
• The earths oceans and continents ride atop of
  the plates.
• Its along the plate boundaries that most
  earthquakes and volcanoes occur due to friction
  and pressure that produces heat.

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Plate Movement

• Plate movement creates oceans and mountain ranges

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Plate Movement

• Continental Drift the theory that the continents
  were once joined and then slowly drifted apart

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Plate Movement

• Pangaea gigantic super continent which
  eventually broke apart

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Ring of Fire

• A circle of volcanic mountains surrounding the
  Pacific Ocean
• It is one of the most earthquake-prone
  volcano-prone areas on the planet.
• Hot Spots are hot regions deep within the mantle
  that produce magma, which rises to the surface.
  Volcanic island chains form as oceanic plates
  drift over the hot spot.
• Example Hawaiian Islands.

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Volcanoes

• Form when magma inside the earth breaks through
  the crust. Lava flows and may produce a large,
  cone-shaped mountain
• They often form along plate boundaries
• Magma splits the earths surface when plates
  collide

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• Faulta break in the earths crust. Movement
  along a fault can send out shock waves, causing
  an earthquake.

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San Andreas Fault
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San Andreas Fault
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• A devastating fire followed the 1906 earthquake
  in San Francisco

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The San Fernando earthquake of 1971 collapsed
freeway overpasses in southern California
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Converging/Collision Zone

• Plates collide and push slowly against each other
  and form a collision or converging zone.
• If 2 oceanic plates collide, 1 slides under the
  other. Islands often form this way.
• If 2 continental plates collide, mountains are
  formed. Example Himalayas

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Continental Crush / Collide
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Spreading Zone

• Plates pull away from each other and form a
  spreading zone.
• These areas are likely to have earthquakes,
  volcanoes, and rift valleys (a large split
  along the crest of a mountain).

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Spreading Zone
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Subduction

• They meet, or CONVERGE and form a subduction
  zone.
• If an oceanic plate collides with a continental
  plate, the heavier oceanic plate will slide under
  the lighter, continental plate.
• This results in volcanic mountain building and
  earthquakes.

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Subduction
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External Forces of Change
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External Forces

• What other forces can create landforms?
• Weathering a process that breaks down rock at
  or near the surface into smaller pieces. This is
  a VERY slow process thousands to millions of
  years.

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• Mechanical Weathering occurs when rock freezes
  it can cause Frost Wedging, a crack in the rock
  caused by freezing.
• Chemical Weathering alters the rocks chemical
  makeup by changing the minerals. This can
  actually change one kind of rock into another.

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• Important forces in Chemical Weathering are
  moisture and carbon dioxide.
• Through this process caves are created.
• Acid Rain causes another type of chemical
  weathering that destroys forests, pollutes water
  and kills wildlife.

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EROSION

• Erosion is the movement of weathered materials
  including gravel, soil and sand.
• The most common agents of erosion are water, wind
  and glaciers.

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Erosion

• Erosion due to wave pounding at Venus Bay, South
  Australia.

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WATER AND EROSION

• Moving Water (rain, rivers, streams and oceans)
  is the greatest agent of erosion.
• Sediment small particles of soil, sand, and
  gravel - are carried by the moving water and
  works like sandpaper to grind away rocks.

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Sediment

• Sediment from the River Rhône flowing into Lake
  Geneva.

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Sediment

• http//www.classzone.com/books/earth_science/terc/
  content/visualizations/es0604/es0604page01.cfm?cha
  pter_novisualization

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Sediment creates new landforms such as
floodplains deltas.

• Deltas form at the mouth of a river

• Floodplains

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Wind Erosion

• The second major cause of erosion is wind,
  especially where there is little water and few
  plants.
• Wind Erosion can devastate one area while
  benefiting another HOW?
• Loess windblown deposits of mineral-rich dust

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GLACIERS CAUSE EROSION?

• Glaciers are slow moving sheets of ice that are
  formed over many years.

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GLACIERS

• How do they cause erosion?
• The movement cuts though land creating lakes.
• They melt away and then rebuild again over
  thousand of years.