Plate tectonics

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Plate tectonics

• Unifying theory of earth science
• Developed from many observations by many
  scientists over a long period of time
• Explains many observations about the Earth

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Jigsaw fit of continents


http//www3.interscience.wiley.com8100/legacy/col
lege/levin/0470000201/chap_tutorial/ch05/images/le
05_24.jpg
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Early evidence Fossil continuity

• Fossil occurrence in rocks continuous across
  different modern continents

http//www.soc.soton.ac.uk/CHD/classroom_at_sea/carls
berg/images/fossil_correlation_lge.jpg
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Ancient glaciations match

• Patterns match up if continents were once together

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Lithospheric Plate Boundaries
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Mountain ranges match
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Mid-ocean ridges
http//dn.redwoods.edu/coursenotes/renner/geo_imag
es/ocean_basins/oceanic_crust_fm_at_ridge.jpg
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Plate Tectonics-Layers of the Earth

• Lithosphere all of the crust and the uppermost
  part of the mantle.
• Brittle - deforms by breaking
• Asthenosphere most of the mantle
• Plastic - deforms by flowing

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Magnetic reversal stripes on ocean floor

• Matching polarities on either side of ridge show
  that all oceanic crust formed at ridge

http//eesc.ldeo.columbia.edu/courses/w4947/html/E
ESC_W4947_Session3_files/image003.gif
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Mantle convection a driving force

• Heat causes material to move upward under
  divergent boundaries
• Cooler material sinks near convergent boundaries

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Seismology Map Earthquake Locations and Depths
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Volcanology Map Recent Volcanic Activity
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Geochronology Map Seafloor Age
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Geography Map Topography and Bathymetry
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1 Nazca / South American
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1 Nazca / South American
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1 Nazca / South American
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1 Nazca / South American
Andes Mountains
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Convergent Subductionoceanic - continental
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2 Indian / Eurasian
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2 Indian / Eurasian
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2 Indian / Eurasian
Tibetan Plateau
Mt. Everest
Himalayan Mtns.
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Convergent Collisioncontinental - continental
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Convergent Collisioncontinental - continental
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3 African / South American
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3 African / South American
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3 African / South American
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3 African / South American
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Divergent midocean ridgeoceanic - oceanic
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4 Australian / Eurasian
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4 Australian / Eurasian
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4 Australian / Eurasian
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4 Australian / Eurasian
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Convergent - Subductionoceanic - oceanic
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5 Pacific / North American
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5 Pacific / North American
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5 Pacific / North American
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5 Pacific / North American
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Transform slidingcontinental - continental
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6 African / Arabian
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6 African / Arabian
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6 African / Arabian
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Divergent Rift

• Continent - continent

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The East African rift a divergent boundary on
land
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