Plate Tectonics - Lemon Bay High School

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Plate Tectonics
Mrs. Mia Conlon
Marine Science
History
• Alfred Wegener hypothesized all the lands were a single
protocontinent called Pangaea
• Pangaea means “all lands” or “all Earth”
• Continental shelves provide the best fit
• Couldn’t provide an excepted mechanism to support until after
death in the 1960’s
Continental Drift
• The theory that the continents move or “drift” relative to each
other
• Wegener was the first to use the term even though the theory had
been around since the 19th century
• Supported by geologic and fossil evidence
• Has been encompassed into plate tectonics
Plate Tectonics
• DEFINITION - scientific theory that describes the large-scale
motion of Earth's lithosphere
• The rigid lithosphere has plates (oceanic & continental crust) that
move above the fluid asthenosphere.
• The movement is caused by convection currents within the
asthenosphere. Material rises as it is heated and falls as it cools
creating a circular pattern and motion.
Supported by
Geologic evidence – matching striations at continental edges
Fossil evidence – matching species along continental edge areas
Paleomagnetism – magnetite and particle orientation
Sea Floor Spreading - Theory of new crust being created at ridge,
pushed away, and returning underneath plate at trenches.
Proposed by Hess in 1960’s
• Heat flow
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Divergent Boundary
Terms for Divergent Boundary
• Lithosphere - the crust plus the rigid, upper mantle.
• Lower Mantle (semi-rigid) - the deepest parts of the mantle, just above the core.
• Magma - molten rock withing the Earth's mantle. In seafloor spreading, magma
moves from the asthenosphere to the crust.
• Ocean - large bodies of water sitting atop oceanic crust.
• Oceanic Crust - thin parts of the Earth's crust located under the oceans.
• Oceanic Ridge - newly-formed region of the oceanic crust.
• Upper Mantle (rigid) - the uppermost part of the mantle, part of the lithosphere.
• Asthenosphere = Upper Mantle (flowing) - the lower part of the upper mantle that
exhibits plastic (flowing) properties. It is located below the lithosphere (the crust
and upper mantle).
Divergent Boundary characteristics
• Plates move apart
• Creates new sea floor
• Mid-ocean ridges
Convergent Boundary
Terms for Convergent Boundary
• Asthenosphere = Upper Mantle (flowing) - the lower part of the upper mantle that exhibits
plastic (flowing) properties. It is located below the lithosphere (the crust and upper mantle).
• Continental Crust - thick parts of the Earth's crust, not located under the oceans.
• Lithosphere - the crust plus the rigid, upper mantle.
• Lower Mantle (semi-rigid) - the deepest parts of the mantle, just above the core.
• Magma - molten rock withing the Earth's mantle. In seafloor spreading, magma moves from
the asthenosphere to the crust.
• Ocean - large bodies of water sitting atop oceanic crust.
• Oceanic Crust - thin parts of the Earth's crust located under the oceans.
• Subduction Zone - the area in which one part of the Earth's crust (a plate) is pushed
underneath another plate as the two plates collide.
• Upper Mantle (rigid) - the uppermost part of the mantle, part of the lithosphere.
• Volcanos - a place on the Earth's surface where molten rock, gases and pyroclastic debris
erupt through the earth's crust.
Convergent Boundary Characteristics
• Plates move towards each other
• Old sea floor is destroyed
• trenches
Transform Boundary
Transform Boundary Characteristics
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Plates move past each other
No destruction or creation of crust
Faults are formed
Numerous types of faults
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