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Plate Tectonics
In This Chapter:
 Composition of the Earth
 Layers of the Earth: crust, outer core, inner core, mantle
 Continental Drift Theory
 Evidence: fossil clues, climate clues, rock clues
 Pangaea
 Theory of Seafloor Spreading
 Evidence: rock and magnetic clues
 Plate Tectonics
 Plate movements
 Plate boundaries
 Convection currents
Fossil Rock Anthem
http://www.youtube.com/watch?v=ClJ5lwl_wM0
Continental Drift Theory
 Proposed by Alfred Wegner
 Continents were at one time all joined together (“Pangaea”)
Pangaea
http://3dparks.wr.usgs.gov/nyc/images/fig83.jpg
Clues to Pangaea
 Fossil Clues
 Reptile Mesosaurus
 Fern Glossopteris
http://www.greatsouth.net/fossil_replicas/images_fossil_replicas/frp100.jpg
http://www.fossilmall.com/EDCOPE_Enterprises/plants/plfossil29/GLOSSOPTERIS-L.jpg
Clues to Pangaea
 Climate Clues
 Fossils of warm water plants found on Arctic Ocean island
(Glossopteris)
 Glacial deposits & grooved bedrock in South America, Africa,
India, and Australia
 These areas were once connected
http://upload.wikimedia.org/wikipedia/commons/thumb/6/67/Pangaea_Glossopteris.jpg/220p
x-Pangaea_Glossopteris.jpg
Clues to Pangaea
 Rock Clues
 Similar rock structures are found on different continents
Ex. Appalachian Mountains:
 Eastern U.S.
 Greenland
 Western Europe
http://www.jamestown-ri.info/Pangaea_mts.jpg
How Do The Continents Drift?
 Theory of Seafloor Spreading supports Wegener’s theory
http://mail.colonial.net/~hkaiter/Aaa_web_images2012/sfsseafloor_spreading.gif
Theory of Seafloor Spreading
 Proposed by Harry Hess in 1960s
 Hot, less dense material in mantle is forced upward to
surface at Mid Ocean Ridge
 It cools, contracts, turns, and flows sideways, carrying the
seafloor away from the ridge in both directions
 MAGMA!
 Moves upward, flows into cracks, solidifies to form new
seafloor
Evidence of Seafloor Spreading
 Age difference in rocks
 Glomar Challenger (research ship) found youngest rocks are
near center of ridges
 Magnetic clues
 Magnetic field has reversed itself
http://www.gcsescience.com/Magnetic-Reversal-Mid-Ocean-Ridge.gif
Plate Tectonics
 Plate movements
 The Earth’s crust and upper mantle are broken into sections
called “plates”
http://www.enchantedlearning.com/egifs/Earthsplates.GIF
Earth’s Composition
 Lithosphere
 Upper mantle and crust
 Rigid, less dense than material below it; divided into plates
 “Floats” on asthenosphere
 Asthenosphere
 Located below lithosphere
 More dense, plastic-like
http://www.physicalgeography.net/fundamentals/images/lithosphere.gif
Plate Boundaries
• Divergent Boundary (divide)
• Plates move away from each other
http://geographicalconcepts.wikispaces.com/file/view/db.jpg/177810579/db.jpg
Plate Boundaries
 Convergent Boundary
 One fault surface is forced up and over the other fault surface
 Forms mountains & subduction zones
http://www.geo.cornell.edu/hawaii/220/PRI/images/subduction2.jpg
Plate Boundaries
 Transform Boundary
 Plates slide past each other
 Not much upward/downward movement
http://www.divediscover.whoi.edu/images/tectonics-slide.jpg
Causes of Plate Tectonics
http://rockdale.k12.ga.us/schools/dms/class/jtamburro/Class%20Documents/Geology%20Unit/Convection%20current.JPG
Effects of Plate Tectonics
 Volcanoes
 Earthquakes
 Mountain building
 Ocean rift formation
 Tsunamis
 Ocean basins
Review
 What are the 3 types of clues for Pangaea?
 Who proposed the Continental Drift Theory?
 What theory did Harry Hess propose?
 What is the difference between the lithosphere and
asthenosphere?
References
Glencoe McGraw-Hill, . Earth Science. 2007. Print.
http://geographicalconcepts.wikispaces.com/file/view/db.jpg/177810579/db.jpg
http://mail.colonial.net/~hkaiter/Aaa_web_images2012/sfsseafloor_spreading.gif
http://rockdale.k12.ga.us/schools/dms/class/jtamburro/Class%20Documents/Geology%20Unit/Convection%20current.JPG
http://upload.wikimedia.org/wikipedia/commons/thumb/6/67/Pangaea_Glossopteris.jpg/220px-Pangaea_Glossopteris.jpg
http://3dparks.wr.usgs.gov/nyc/images/fig83.jpg
http://www.divediscover.whoi.edu/images/tectonics-slide.jpg
http://www.enchantedlearning.com/egifs/Earthsplates.GIF
http://www.fossilmall.com/EDCOPE_Enterprises/plants/plfossil29/GLOSSOPTERIS-L.jpg
http://www.gcsescience.com/Magnetic-Reversal-Mid-Ocean-Ridge.gif
http://www.geo.cornell.edu/hawaii/220/PRI/images/subduction2.jpg
http://www.greatsouth.net/fossil_replicas/images_fossil_replicas/frp100.jpg
http://www.jamestown-ri.info/Pangaea_mts.jpg
http://www.physicalgeography.net/fundamentals/images/lithosphere.gif
http://www.youtube.com/watch?v=ClJ5lwl_wM0