Guided Notes on the Theory of Plate Tectonics

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Guided Notes on the Theory of Plate Tectonics

• Chapter 17, Section 3

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1. State the theory of plate tectonics in its
entirety

• The earths crust and rigid upper mantle are
  broken into enormous slabs called plates. These
  plates move in different directions and at
  different speeds and this movement is caused by
  the Earths internal heat.

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2. What are the 3 types of movement that can
occur at plate boundaries?

• Plates can come together, or converge
• Plates can move away from each other, or diverge
• Plates can move horizontally past each other

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• 3. Divergent boundaries are places where 2
  tectonic plates are moving apart. Most divergent
  boundaries are found on the seafloor, where they
  form ocean ridges.

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• 4. The process of seafloor spreading along a
  divergent boundary may cause an ocean basin to
  grow wider.

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• 5. A divergent boundary formed on a continent is
  called a rift valley, which is a long narrow
  depression in continental crust.

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• 6. Convergent boundaries are places where 2
  tectonics plates are moving toward each other.

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3 Types of Convergent Boundaries

• Continental-Continental
• One continental plate converges with another
  continental plate. Neither plate is forced
  downward and a folded mountain range is formed.

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3 Types of Convergent Boundaries

• 2. Oceanic-Oceanic
• Oceanic crust converges with oceanic crust. One
  plate is forced downward, resulting in a deep-sea
  trench and an island arc of volcanoes.

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3 Types of Convergent Boundaries

• Oceanic-Continental
• An oceanic plate converges with a continental
  plate and the oceanic plate is forced downward.
  A trench forms along with a volcanic mountain
  range on the edge of the continent

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What is subduction?

• Subduction is the process of one crustal plate
  descending beneath another.

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Where does it occur?

• Subduction occurs at a subduction zone, where one
  plate descends beneath another.

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How does it happen?

• If one oceanic plate becomes denser than another
  plate (because it is cooler), then it will
  descend below the other plate as they converge.

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What forms as a result of it?

• A deep-sea trench and an island arc of volcanoes
  form at subduction zones.

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When subduction occurs between a continental and
oceanic plate

• When an oceanic and continental plate converge,
  the oceanic plate is subducted because it is
  denser.
• A trench is formed along the coast of the
  continent, along with a series of volcanoes along
  the edge of the continental plate.

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• 10. When two continental plates converge, the
  colliding edges of the continents are crumpled
  and uplifted to form a mountain range.

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• 11. A transform boundary is a place where two
  plates slide horizontally past each other.

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12. What happens to crust at a transform boundary?

• Crust is only deformed or fractured. It is
  neither subducted or uplifted. Transform
  boundaries are characterized by long faults and
  shallow earthquakes.