Plate Tectonics

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Plate Tectonics

• Earth on the move

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Lyells breakthrough. Uniformitarianism
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Uniformitarianism (notes)

• Uniformitarianism The forces active today are
  the forces that were active in the past.
• The present is the key to the past concept
  developed by Charles Lyell
• Leads to the understanding that the Earth that is
  many millions of years old.

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Alfred Wegeners Evidence for Continental Drift
(circa 1915 AD)

• The same Fossils of animals and plants in distant
  continents.
• Ancient mountains, glaciers and coal deposits
  become continuous once continents are put back
  together again
• Identical sedimentary rocks found in identical
  layers at remote regions of the world
• Look on page 21 of text.

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Alfred Wegeners Theory of Continental Drift

• Makes a theory for the continents once having
  been together in a super-continent called PANGAEA
  
• BUT, he has no mechanism or explanation for what
  could move the massive continents.

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-60 C (-76 F)
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• Six months later, on May 12, 1931, Wegener's body
  was found halfway between Eismitte and West camp.
  It had been buried (by Villumsen) with great care
  and a pair of skis marked the grave site. Wegener
  had been fifty years of age and a heavy smoker
  and it was believed that he had died of heart
  failure brought on by overexertion. His body was
  reburied in the same spot by the team that found
  him and the grave was marked with a large cross.,

• Published in 1915

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What is this?How do we know it existed
Mid Atlantic Ridge
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From Space
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Paleomagnetism
Paleomagnetic info from the sea floor (page 27)
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Plate Boundaries

• We have discovered 3 types of plate movement
• All three can cause Earthquakes
• Divergent ( plates moving apart)
• mid-ocean ridges, new ocean floor and rift
  valleys form from these
• Convergent (move together) ocean trenches and
  most mountains form from these
• Transform (or) Strike Slip Boundaries (move side
  to side) Only form earthquakes.

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Divergent Boundary
Rift Valley
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Two types of Convergent Plate boundaries

• The boundary where the two continental plates
  meet is called a COLLISIONARY boundary.
• Creates Folded mountains and earthquakes

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Subduction Boundary

• A special type of convergent plate boundary
• In locations around the world, ocean crust
  subducts, or slides under, a continental plate.
• This creates the geologic features we see below

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Subduction in Action
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Transform boundaries Or A Strike Slip fault
(also called a lateral fault), They dont create
or consume crust. Rather, two plates move against
each other, building up force, then releasing
this force in a sudden and often violent jerk.
This sudden jerk creates an earthquake.
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Earths Weather is Created by Convection Cells
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Convection Cells are what power plate movement.
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Do you know whats happening here?
Is that happening in this picture as well?
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