Chapter 4 Section 3

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Chapter 4 Section 3

• Theory of Plate Tectonics

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Language of the discipline

• lithospheric plate a large brittle piece of
  Earths outer shell
• plate tectonics theory that explains how
  lithospheric plate move and cause major geologic
  features and events on Earths surface
• ocean trench long, deep parts of the seafloor
• Slab plate that sinks back into the mantle
• Global Positioning System (GPS) a network of
  satellites used to determine locations on
  Earth

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Language of the discipline continue

• Convection heat transfer by the movement of
  matter from one place to another
• Define to fix or mark the limits of

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Earths Plates

• Lithospheric plates are large brittle pieces of
  Earths outer shell.
• The theory of plate tectonics explains the
  movement of lithospheric plates.

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Boundaries of Lithospheric Plates

• Mid-ocean ridges show boundaries of some
  lithospheric plates
• .

• Earthquakes and volcanoes occur where the edges
  of plates are pushed together, pulled apart, or
  slide horizontally.
• Ocean trenches are the deep parts of the seafloor
  where numerous earthquakes and volcanoes occur.
• Seafloor is formed at ridges and destroyed at
  ocean trenches.

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Boundaries of Lithospheric Plates (cont.)
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Types of Lithosphere

• Oceanic Crust thinner than continental, made of
  dense igneous rock covered by a thin layer of
  sediment (sand dirt)
• Continental Crust thicker than oceanic made of
  igneous and metamorphic rock covered by
  sedimentary rock

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What controls plate movement?

• Some scientists believe that convection controls
  the movement of plates.

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What controls plate movement? (cont.)

• Temperature increases with increasing depth.
• Radioactive decay is one important source of
  internal heat.
• Heat increases the temperature of rock which
  decreases the density.

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Plate Movement and Convection

• Slabs are cooler, denser lithospheric plates that
  sink down into the mantle.
• They bend and break as they sink down into the
  mantle, causing earthquakes.

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Ridge Push and Slab Pull

• Convection Cooler, denser masses of rock sink,
  bringing plates with them. Less-dense rock is
  brought to the surface at mid-ocean ridges.
• Ridge Push The force of gravity moves the plate
  downward and away from the mid-ocean ridges.
• Slab Pull Gravity acts on denser plates,
  pulling them into the mantle.

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Ridge Push and Slab Pull
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Plate Movement

• Global Positioning System (GPS) is a network of
  satellites using radio waves to determine
  locations on Earth.
• Measures the movement of plates
• Using GPS and satellite laser ranging (SLR),
  plate movement has been estimated at a few
  centimeters per year.

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GPS Satellite Laser Ranging in Plate Tectonics

• GPS (Global Positioning System) is a network of
  satellites that uses radio waves to measure the
  direction and speed of plates as they move along
  Earths surface.
• Satellite Laser Ranging (SLR) uses laser beams to
  measure the distances of plate movements.

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Checking for Understanding

• 1. What does the theory of plate tectonics
  explain?
• 2. What two types of lithosphere make up Earths
  surface ?
• 3. Why does the density of the surrounding rock
  decrease (Think slabs?)
• 4. What are GPS?
• 5. Use the term slab and ocean trench in a
  sentence.
• 6. A method used to determine the rate of plate
  movement is ______.
• 7. On the back of your paper draw a compare and
  contrasting thinking map of the following
  Convection, Ridge Push, and Slab Pull.