Chapter 4 Plate Tectonics

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Chapter 4 Plate Tectonics

• By Diana Smith

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Section 1 Inside the Earth

• There are 3 main parts of the earth
• Crust
• Mantle
• Core

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The Crust

• Outermost layer
• 5 to 100 km thick
• Continental crust less dense, but thicker
• Oceanic Crust more dense, but thinner

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The Mantle

• The layer between the crust and the core
• Most of earths mass
• Extremely thick (2,900 km thick)
• Clues gained from volcanoes

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The Core

• Outer core
• Made of liquid
• 2,200 km thick
• Inner core
• Solid, dense layer
• 1,228 km thick
• Made mostly of iron and nickel

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Layers of the earth

• In order from outside in
• Lithoshpere
• Asthenosphere
• Mesosphere
• Outer Core
• Inner Core

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Lithosphere

• Outermost rigid portion of the earth
• Made of two parts
• Crust
• Rigid upper portion of the mantle
• Divided into tectonic plates

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Asthenosphere

• Weak sphere
• Soft layer of the mantle on which pieces of the
  lithosphere move
• Made of solid rock that flows like putty

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Mesosphere

• Strong, lower part of the mantle
• middle sphere

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Tectonic Plates

• Pieces of lithosphere that move around on top of
  asthenosphere
• 10 major tectonic plates
• We live in North American Plate

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Tectonic Plates

• Fit together like pieces of a jigsaw
• Plates are thicker below the surface than the
  features (like mountains), show above
• Both continental and oceanic crusts are less
  dense than the asthenosphere below, and therefore
  float

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Mapping Earths interior

• Seismic waves from earthquakes help scientists to
  map the inner densities and thicknesses of the
  earth

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Review

• What is the difference between continental and
  oceanic crust?
• How is the lithosphere different from the
  asthenosphere?
• How do scientists know about the structure of the
  Earths interior?
• Explain the difference between the crust and the
  lithosphere.