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Plate Tectonics
Alfred Wegener
Published The Origin of Continents and Oceans (1915)
Father of “Continental Drift”
Evidence for Plate Tectonics
Jigsaw Fit of Continental Shelves
Mesosaurus (Late Paleozoic to Early Mesozoic)
Evidence for Plate Tectonics
Fossil Correlation Across Seas
Evidence for Plate Tectonics
Rock Correlation Across Seas
Evidence for Plate Tectonics
Rock Correlation Across Seas
Differences in Ancient Climates
Evidence for Plate Tectonics
Glacial Imprints in Rocks in Tropics
WW2 – Sonar – mapping seafloor
North Pole
South Pole
Magnetite (Fe3O4)
Minerals retain their magnetic moment when they are cooled below the Curie Temperature
Magnetic Reversals North
South
Magnetic Reversal
s Through Geologic
Time
Magnetic Polarity Time Scale established back to about 180 million yrs
Earth’s Magnetic Flux Lines
Intensity of Magnetism
N
S
Magnetic Stripes on the
Seafloor
Age of seafloor determined – led to acceptance of Plate Tectonics
15 Tectonic Plates
Tectonic Motions
Location of World’s Major Volcanoes
Lithosphere – The rigid outer layer of the Earth, including the crust and part of the upper mantle
Asthenosphere – The portion of the upper mantle below the lithosphere that is easily deformed
Subduction
The thrusting of oceanic plate into the
mantle at a plate boundary
Continent-Ocean Plate Orogeny
Juan de Fuca Plate
Mt. St. Helens, Before 1980
Ocean-Ocean Plate Orogeny
Many mountain belts are built by Ocean-Continent AND
Continent-Continent collisions.
Mountain Building (Orogenesis)
Continent-Continent Collisions
Continent-Continent Orogeny
Mt. Makalu, Nepal
Divergent plate boundaries
Birth of an Ocean at
a Divergent
Margin
Transform (or Strike-Slip) Faults
San Andreas:
A Transform Fault on Land
Hot Spots
Tectonic Motions
Convection
The transfer of heat by
the movement of
matter.
Convection Cell
Double-Layer Convection
Depressurized Melting
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