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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.
“I say.” “Africa and South
America fit strangely like
two puzzle pieces.”
Copyright © 2010 Ryan P. Murphy
• In 1915, The German geologist Alfred Wegener
(1880-1930) proposed continental drift. Not
accepted until the 1950’s!
Copyright © 2010 Ryan P. Murphy
• 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.
Copyright © 2010 Ryan P. Murphy
• Same fossils found on different continents
– These are the pictures on the puzzle pieces.
Copyright © 2010 Ryan P. Murphy
• 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?
Copyright © 2010 Ryan P. Murphy
• Answer! This is a fossilized tropical plant
found on Antarctica.
Copyright © 2010 Ryan P. Murphy
• Answer! This is a fossilized tropical plant
found on Antarctica.
– Remember, the continents have moved and
Antarctica use to be in a warmer climate.
Copyright © 2010 Ryan P. Murphy
• 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.
Copyright © 2010 Ryan P. Murphy
– Gondwondaland and Laurasia were two mega
continents after Pangea.
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• Current Day + or – 4mm
• What causes continental drift and plate
tectonics?
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
• Answer!
– Convection currents (Remember heat rises) move
the plates
Copyright © 2010 Ryan P. Murphy
Video! Plate Tectonics
• Layers of the earth
Copyright © 2010 Ryan P. Murphy
• Layers of the earth
Copyright © 2010 Ryan P. Murphy
• Layers of the earth
Copyright © 2010 Ryan P. Murphy
• Layers of the earth
Copyright © 2010 Ryan P. Murphy
• Layers of the earth
Copyright © 2010 Ryan P. Murphy
• 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.
Copyright © 2010 Ryan P. Murphy
• Inner Core: Solid Iron and Nickel (Dense).
Copyright © 2010 Ryan P. Murphy
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.
Copyright © 2010 Ryan P. Murphy
• Outer Core: Liquid Iron and Nickel
Copyright © 2010 Ryan P. Murphy
• Mantle: Composed of Magnesium Silicates,
Iron, Calcium
Copyright © 2010 Ryan P. Murphy
• Mantle: Composed of Magnesium Silicates,
Iron, Calcium
- Outer Mantle (Asthenosphere)
Copyright © 2010 Ryan P. Murphy
• Mantle: Composed of Magnesium Silicates,
Iron, Calcium
- Outer Mantle (Asthenosphere)
- Lithosphere (Crust)
Copyright © 2010 Ryan P. Murphy
• Review! Heat from the earth rises and run
along plates causing them to move.
Copyright © 2010 Ryan P. Murphy
• New Area of Focus: Earth’s Plate Boundaries.
Copyright © 2010 Ryan P. Murphy
• 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.
Copyright © 2010 Ryan P. Murphy
Newer
Newer
Older
Newer
Newer
Older
Older
Newer
Newer
Older
Older
Newer
4 miles thick
Newer
Older
• Convergent Boundaries: Crust is destroyed
and recycled back into the interior of the
earth.
– One plate dives under another.
Copyright © 2010 Ryan P. Murphy
• Convergent Boundaries: Crust is destroyed and
recycled back into the interior of the earth.
– One plate dives under another.
Copyright © 2010 Ryan P. Murphy
• Ocean vs. Continent (Subduction zone)
Copyright © 2010 Ryan P. Murphy
• 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.
Copyright © 2010 Ryan P. Murphy
• Many tropical Islands like this are created by
ocean plates and volcanism.
Copyright © 2010 Ryan P. Murphy
Copyright © 2010 Ryan P. Murphy
Copyright © 2010 Ryan P. Murphy
Ocean Plate
Ocean Plate
Ocean Plate
Ocean Plate
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Volcanic Arch Island
Chain / Archipelago
Ocean Plate
Ocean Plate
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• 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).
Copyright © 2010 Ryan P. Murphy
• 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
Copyright © 2010 Ryan P. Murphy
• Antilles in Caribbean
• Aleutian Islands Alaska
• Indonesia – Every triangle is a volcano