Theory of Plate
Tectonics ll
By: Enrico Romeo F. Abanales
References: whybecausescience.com
What evidences do we now have for the
Theory of Plate Tectonics?
Fossil Distribution
• existence of plate tectonics
• discovery of very similar fossils
Examples:
India: Triassic land reptile; Lystrosaurus
South America: Triassic land reptile; Cynognathus
Freshwater reptile; Mesosaurus
Antartica: fern; Glossopteris
References: http://hyperphysics.phy-astr.gsu.edu/hbase/geophys/platevid.html
Lystrosaurus fossil
References: en.wikipedia.org
Cynognathus
References: www.snipview.org
Mesosaurus
References: commons.wikimedia.org
Glossopteris fossil
References: commons.wikimedia.org
Paleomagnetism
• Iron-rich magnetic minerals
• Magnetite
• present in basaltic lava flow
• Ferromagnetism
• Curie temperature; 1043K
• 850 K (580°C); magnetite
• Solidifying
• slightly magnetized
• direction of Earth's magnetic field
References: http://hyperphysics.phy-astr.gsu.edu/hbase/geophys/platevid.html
What drives the plates?
• Harry Hess' theory
• plate-driving force
• slow movement of hot, softened mantle
• rigid plates
• 1930s by Arthur Holmes
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English geologist
seafloor spreading
circular motion
continents
conveyor belt
References: http://pubs.usgs.gov/gip/dynamic/unanswered.html
• Earth; solid, motionless body
• J. Tuzo Wilson
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1968
"The earth, instead of appearing as an inert statue, is a living, mobile thing."
Earth's surface
interior
• lithospheric plates
• mantle
• molten
• steady forces
References: http://pubs.usgs.gov/gip/dynamic/unanswered.html
Slab Pull
• Slab Pull
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subducting plate
mantle
primary force
collisional zones (Wilson, 1993)
• slab pull force
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subducting slab
circulation patterns
mantle
dominant force (Conrad and Lithgow-Bertelloni, 2002)
References: http://www.geosci.usyd.edu.au/users/prey/ACSGT/EReports/eR.2003/GroupD/Report1/web%20pages/Driv_tectonics
.html
References: www.haikudeck.com
Ridge Push
• leading contributor
• slab pull
• slab pull acting
• two main models of ridge push
• Bott (1991)
• 'gravity wedging'
• 'gravity sliding‘
• dominant model
References: http://www.geosci.usyd.edu.au/users/prey/ACSGT/EReports/eR.2003/GroupD/Report1/web%20pages/Driv_tectonics
.html
Ridge Push
References: www.haikudeck.com
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