plate tectonics 7 th grade science. area of focus: plate tectonics copyright © 2010 ryan p. murphy
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Plate Tectonics 7th Grade Science
• Area of Focus: Plate Tectonics
Copyright © 2010 Ryan P. Murphy
• Plate tectonics: The earth’s crust and upper mantle are broken into sections called plates. – These plates float on the mantle like rafts (moving
very slowly)
Copyright © 2010 Ryan P. Murphy
• Plate tectonics: The earth’s crust and upper mantle are broken into sections called plates. – These plates float on the mantle like rafts (moving
very slowly)
Copyright © 2010 Ryan P. Murphy
• Continental Drift: The gradual movement of the continents across the earth.
Copyright © 2010 Ryan P. Murphy
• The speed at which the plates move is about the speed at which your fingernails grow.
Copyright © 2010 Ryan P. Murphy
• Video! How did the continents form?
• In 1915, The German geologist Alfred Wegener (1880-1930) proposed continental drift.
Copyright © 2010 Ryan P. Murphy
• In 1915, The German geologist Alfred Wegener (1880-1930) proposed continental drift.
Copyright © 2010 Ryan P. Murphy
“I say.” “Africa and South America fit strangely like two puzzle pieces.”
• In 1915, The German geologist Alfred Wegener (1880-1930) proposed continental drift. Not accepted until the 1950’s!
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• Evidence for continental drift.– -– -– -– - – -
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• The shapes match.
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• Same fossils found on different continents– These are the pictures on the puzzle pieces.
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• Same fossils found on different continents– These are the pictures on the puzzle pieces.
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• The Same rock structures on different continents
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• What is this a fossil of?– Where would you expect to find a specimen like
this on the planet?
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• Answer! This is a fossilized tropical plant found on Antarctica.
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• Answer! This is a fossilized tropical plant found on Antarctica.– Remember, the continents have moved and
Antarctica use to be in a warmer climate.
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• Fossils of plants and animals in Antarctica
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• Behold the Supercontinent! Pangea
?
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• Behold the Supercontinent! Pangea
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• Pangea: The “Super Continent” – All of the plates were once together.
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• Pangea: The “Super Continent” – All of the plates were once together.
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– Gondwondaland and Laurasia were two mega continents after Pangea.
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• Current Day + or – 4mm
• What causes continental drift and plate tectonics?
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• Answer! – Convection currents (Remember heat rises) move
the plates
Copyright © 2010 Ryan P. Murphy
• Answer! – Convection currents (Remember heat rises) move
the plates
Copyright © 2010 Ryan P. Murphy
• Answer! – Convection currents (Remember heat rises) move
the plates
Copyright © 2010 Ryan P. Murphy
• Answer! – Convection currents (Remember heat rises) move
the plates
Copyright © 2010 Ryan P. Murphy
Video! Plate Tectonics
• Layers of the earth
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• Layers of the earth
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• Layers of the earth
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• Layers of the earth
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• Layers of the earth
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• Layers of the earth
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• Earth’s layers formed early in it’s long history.
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• Earth’s layers formed early in it’s long history.– (Archean Eon) Gravity pulled heavy elements
toward the middle.
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• Inner Core: Solid Iron and Nickel (Dense).
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Hot and Dense
Less Hot and Dense
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• The spinning inner cores of solid and liquid Iron creates a giant electromagnetic field.
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• Outer Core: Liquid Iron and Nickel
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• Mantle: Composed of Magnesium Silicates, Iron, Calcium
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• Mantle: Composed of Magnesium Silicates, Iron, Calcium
- Outer Mantle (Asthenosphere)
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• Mantle: Composed of Magnesium Silicates, Iron, Calcium
- Outer Mantle (Asthenosphere)- Lithosphere (Crust)
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• Review! Heat from the earth rises and run along plates causing them to move.
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• New Area of Focus: Earth’s Plate Boundaries.
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• Two types of Crust– -– -
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• Oceanic Crust: More dense so it sinks more (Basalts).
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• Continental Crust: Less Dense so it floats higher (Granites)
Copyright © 2010 Ryan P. Murphy
• Which plates below are ocean plates?
• Answer! Nazca Plate.
• Answer! Pacific Plate
• Answer!
• Answer!
• Activity! Using Google Earth to look at divergent ocean plate boundaries on the sea floor.– http://www.google.com/earth/index.html
• Divergent Boundaries: Crust is created as two or more plates pull away from each other.
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Newer Newer
Newer NewerOlder Older
Newer NewerOlder Older
Newer NewerOlder Older
4 miles thick
• Convergent Boundaries: Crust is destroyed and recycled back into the interior of the earth.– One plate dives under another.
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• Convergent Boundaries: Crust is destroyed and recycled back into the interior of the earth.– One plate dives under another.
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• Ocean vs. Continent (Subduction zone)
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• Ocean vs. Continent (Subduction zone)– The oceanic plate is forced below the continental
plate.
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• What is the “Ring of Fire”?
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• What is the “Ring of Fire”?
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• Ring of Fire: A zone of frequent earthquakes and volcanic eruptions that encircles the basin of the Pacific Ocean.
Copyright © 2010 Ryan P. Murphy
• Ring of Fire: A zone of frequent earthquakes and volcanic eruptions that encircles the basin of the Pacific Ocean.
Copyright © 2010 Ryan P. Murphy
• Ring of Fire: A zone of frequent earthquakes and volcanic eruptions that encircles the basin of the Pacific Ocean.
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• Many tropical Islands like this are created by ocean plates and volcanism.
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Copyright © 2010 Ryan P. Murphy
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Ocean Plate
Ocean Plate
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Ocean Plate
Ocean Plate
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Ocean Plate
Ocean Plate
Volcanic Arch Island Chain / Archipelago
• Video Link! New volcanic island forming– http://www.youtube.com/watch?v=kwETZSARMg
E
• Transform-Fault Boundaries: Where two plates are sliding horizontally past one another.
Copyright © 2010 Ryan P. Murphy
• Coastal California and the Baja Peninsula will become an Island.
• Coastal California and the Baja Peninsula will become an Island.
• Coastal California and the Baja Peninsula will become an Island.
• Continental Convergence: (Mountain Building).
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• The Swiss Alps is an example of mountains that form when continents collide.– The African Plate is colliding with the European Plate
• The Swiss Alps is an example of mountains that form when continents collide.– The African Plate is colliding with the Eurasian plate/
• Indian Continental Plate is crashing into Asian Plate causing the mountains to form. – They are still growing.
Copyright © 2010 Ryan P. Murphy
• Himalayas: Tallest Mountains on Earth.
• Continent Divergence (Moving apart).
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• Ocean vs. Ocean Convergence
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• Antilles in Caribbean
• Aleutian Islands Alaska
• Indonesia – Every triangle is a volcano
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