Plate Tectonics

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Plate Tectonics
http//www.learner.org/interactives/dynamicearth/i
mages/new_map.jpg
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Tectonic Plates

• The Earths crust is made of many gigantic plates
  that move as they float on the mantle.
• According to the theory of continental drift, the
  plates are moving.
• Europe and North America are thought to be moving
  away from each other 3cm each year.
• Other plates are moving toward each other and
  some are sliding against each other.
• Wherever plates meet, earthquakes signal their
  movement.

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Tectonic Plates
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Pangaea

• Have you ever noticed that the continents look
  like puzzle pieces?
• In 1912, Alfred Wegener suggested that millions
  of years ago the continents were all part of one
  big continent called Pangaea.

http//upload.wikimedia.org/wikipedia/commons/1/16
/Wegener_Expedition-1930_008.jpg
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Pangaea
http//azgenweb.org/navajo/History/Petrified/Panga
ea_continents.png
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Continental Drift

• Wegener suggested that Pangaea had broken apart
  and that the continents had and still are
  drifting apart.
• This theory is called Continental Drift
• At the time, Wegeners theory was dismissed as he
  had no evidence besides the fact that the
  continents fit together.

http//newpangaea.eu/sitebuildercontent/sitebuilde
rpictures/Pangaea.JPG
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The Evidence

• Certain fossils of extinct reptiles found only in
  Africa and South America.
• Fossils of plants and animals found in
  Antarctica, which is now inhabitable.
• Rocks similar in age and type found along the
  coasts of continents that fit together.

http//www.lostrivers.ca/points/pangaea.gif
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Plate Tectonics Theory

• Theory that states that the Earths crust is made
  up of several large sections called plates.
• These plates are slowly moving, floating on top
  of the Earths mantle.
• Continents drift by riding on top of the plates.

http//www.geography-site.co.uk/pages/physical/ear
th/images/plates.gif
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Sliding-By Plates

• When two plates slide against each other, a fault
  is formed.
• The plates do not collide or separate they just
  slip by.
• Ex) The San Andreas Fault in California.

http//lacreekfreak.files.wordpress.com
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Plate Collisions

• When two plates collide, one plate usually
  plunges below into the hot mantle where it heats
  up and melts.
• This process is called subduction.

http//whyfiles.org/031volcano/images/subduction.g
if
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Separating Plates

• When two plates move apart, magma from the mantle
  rises up into the crack between the two plates
  and hardens.
• This forms ridges of new rock.
• Ridges usually form under the ocean but does
  occur in Iceland also.

http//www.utexas.edu/tmm/npl/mineralogy/blowups/o
ceanicridge.jpg