PLATE TECTONICS

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• PLATE TECTONICS
• AND
• CONTINENTAL DRIFT

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GEOLOGY

• Geology is the science and study of the solid
  Earth and the processes by which it is shaped and
  changed.
• Geologists are scientists who study the forces
  that make and shape the planet Earth.

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Theory of continental drift

• Alfred Wegener first proposed the theory of
  continental drift in 1912.
• Continental drift is Wegeners theory that all
  continents had once been joined together in a
  single landmass and have drifted apart since.
• Wegener named this supercontinent Pangaea.
• Wegeners theory was rejected by scientists
  because he could not explain what force pushes
  or pulls continents.

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PANGEA
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Evidence to support continental drift theory

• Sequence of Rocks
• Same rock patterns found in South America, India,
  Africa, Antarctica and Australia

• Ancient Climates
• Tropical plant remains found in Antarctica
• Glaciations in Africa, South America, India, and
  Australia during the same time

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Evidence to support continental drift theory

• Distribution of Fossils
• Plant and animal fossils found on the coastlines
  of different continents

• Puzzle Pieces
• Continents look like they could be part of a
  giant jigsaw puzzle

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Sea-Floor Spreading

• In the early 1960s, Princeton geologist Harry
  Hess proposed the hypothesis of sea-floor
  spreading, in which magma from the mantle rises
  to create new ocean floor at mid-ocean ridges.
• The mid-ocean ridge is the longest chain of
  mountains found deep below the oceans surface .

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SUBDUCTION

• The ocean floor plunges into deep underwater
  canyons called deep-ocean trenches.
• Subduction takes place in deep-ocean trenches.
• Subduction is the process by which the ocean
  floor sinks beneath a deep-ocean trench and back
  into the mantle.

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PLATE TECTONICS

• The Earths crust is divided into 12-13 major
  plates which are moved in various directions.

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Plate Movement

• Plates of lithosphere are moved around by the
  underlying hot mantle convection cells

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3 types of plate boundaries

• Divergent
• Convergent
• Transform

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DIVERGENT BOUNDARY

• At divergent boundaries, two plates move apart
  from each other and the space that this creates
  is filled with new crustal material sourced from
  molten magma that forms below.

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CONVERGENT BOUNDARY

• A tectonic boundary where two plates are moving
  toward each other. If the two plates are of equal
  density, they usually push up against each other,
  forming a mountain chain. If they are of unequal
  density, one plate usually sinks beneath the
  other in a subduction zone.

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There are 3 types of convergent plate boundaries

• Continent Continent When two continents meet
  head-on, neither is subducted because the
  continental rocks are relatively light. (forms
  mountains)
• Ocean Continent When an oceanic plate pushes
  into and subducts under a continental plate (
  creates volcanoes)
• Ocean Ocean When two oceanic plates converge
  one is usually subducted under the other. (forms
  trenches)

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Oceanic-continental

• Continental-continental
• Oceanic-oceanic

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TRANSFORM FAULT BOUNDARY

• Transform Plate Boundaries are locations where
  two plates slide past one another. The fracture
  zone that forms a transform plate boundary is
  known as a transform fault.

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