updatedcreated by c. ippolito april 2009 plate tectonics theory that describes the formation,...
TRANSCRIPT
Updated Created by C. IppolitoApril 2009
Plate Tectonics
theory that describes the formation, movement, and interactions of lithosphere sections that move over the athenosphere
Updated Created by C. IppolitoApril 2009
Early Ideas About Plate Movements
• 1596– Dutch mapmaker suggested Africa and South
America may have been one continent
• 1912 Alfred Wegener– Continental Drift
• hypothesis that continents had drifted or moved
– Mesosaurus found eastern S.A. & western Africa
– rock formations matchup• Pangea
– single “super continent”
Updated Created by C. IppolitoApril 2009
Permian Era (225 mya)
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Triassic (200 mya)
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Jurassic (135 mya)
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Cretaceous (65 mya)
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Present Day
Updated Created by C. IppolitoApril 2009
Theory of Plate Tectonics
• Capt. H. H. Hess– believed Wegener– echo soundings of ocean floor
• mapped midocean ridges– younger rocks at “rifts”– older rocks on sides
– presented sea floor spreading mechanism (1960’s)
– located deep sea trenches• continental mtns (Andes)• island arcs (Japan, Aleutians)
Updated Created by C. IppolitoApril 2009
Other Evidence for Plate Tectonic Theory
• Worldwide distribution of volcanoes• Worldwide distribution of earthquakes• Age of rocks at rifts• Paleomagnetic “stripes” are symmetrical
about ridges – confirming seafloor spreading
Updated Created by C. IppolitoApril 2009
Basic Concepts
• Lithosphere (upper mantle + crust)– made of rigid plates
• Plates move slowly• Geologic activity at or near boundaries• Interior of plates “quiet”
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Types of Plate Boundaries
• Divergent Boundary– move away from each other
• Convergent Boundary– move toward each other
• Transform Boundary– move past each other
Updated Created by C. IppolitoApril 2009
Divergent Boundary
• plates move apart– mantle convection
• Mid Atlantic Ridge• East Pacific Rise
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Convergent Boundary
• plates moving toward each other– Subduction Boundary
• one plate moves under the other– ocean-ocean
» deep sea trenches» island arcs
– ocean-continent» coastal volcanoes
– Collision Boundary• plates push against each other form mtns
– continent-continent» Himalays
Updated Created by C. IppolitoApril 2009
Transform Boundary
• plates slide past each other– earthquake activity
• San Andreas Fault• North Anatolian Fault (Turkey)
Updated Created by C. IppolitoApril 2009
Causes of Plate Movement
• Mantle Convection– Magma hotter and less dense at ridge– As it rises and moves away it pulls plate
• Ridge Push– New formed rock cools/is more dense– Gravity has it “slide” away from ridge
• Slab Pull– At subduction zone denser plate “pulls
down”