Plate Tectonics 7 th Grade Science. Area of Focus: Plate Tectonics Copyright © 2010 Ryan P. Murphy

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)


• 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)


• Continental Drift: The gradual movement of the continents across the earth.


• The speed at which the plates move is about the speed at which your fingernails grow.


• Video! How did the continents form?

• In 1915, The German geologist Alfred Wegener (1880-1930) proposed continental drift.


• In 1915, The German geologist Alfred Wegener (1880-1930) proposed continental drift.


“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!


• Evidence for continental drift.– -– -– -– - – -


• The shapes match.


• Same fossils found on different continents– These are the pictures on the puzzle pieces.


• Same fossils found on different continents– These are the pictures on the puzzle pieces.


• The Same rock structures on different continents


• What is this a fossil of?– Where would you expect to find a specimen like

this on the planet?


• Answer! This is a fossilized tropical plant found on Antarctica.


• Answer! This is a fossilized tropical plant found on Antarctica.– Remember, the continents have moved and

Antarctica use to be in a warmer climate.


• Fossils of plants and animals in Antarctica


• Behold the Supercontinent! Pangea

?


• Behold the Supercontinent! Pangea


• Pangea: The “Super Continent” – All of the plates were once together.


• Pangea: The “Super Continent” – All of the plates were once together.


– Gondwondaland and Laurasia were two mega continents after Pangea.


• Current Day + or – 4mm

http://antwrp.gsfc.nasa.gov/apod/image/0010/PangeaUltima_scotese_big.jpg

• What causes continental drift and plate tectonics?


• Answer! – Convection currents (Remember heat rises) move

the plates



the plates



the plates



the plates


Video! Plate Tectonics

• Layers of the earth












• Earth’s layers formed early in it’s long history.


• Earth’s layers formed early in it’s long history.– (Archean Eon) Gravity pulled heavy elements

toward the middle.


• Inner Core: Solid Iron and Nickel (Dense).


Hot and Dense

Less Hot and Dense


• The spinning inner cores of solid and liquid Iron creates a giant electromagnetic field.


• Outer Core: Liquid Iron and Nickel


• Mantle: Composed of Magnesium Silicates, Iron, Calcium



- Outer Mantle (Asthenosphere)



- Outer Mantle (Asthenosphere)- Lithosphere (Crust)


• Review! Heat from the earth rises and run along plates causing them to move.


• New Area of Focus: Earth’s Plate Boundaries.


• Two types of Crust– -– -


• Oceanic Crust: More dense so it sinks more (Basalts).


• Continental Crust: Less Dense so it floats higher (Granites)


• 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

http://www.google.com/earth/index.html

• Divergent Boundaries: Crust is created as two or more plates pull away from each other.


Newer Newer

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.


• Convergent Boundaries: Crust is destroyed and recycled back into the interior of the earth.– One plate dives under another.


• Ocean vs. Continent (Subduction zone)


• Ocean vs. Continent (Subduction zone)– The oceanic plate is forced below the continental

plate.


• What is the “Ring of Fire”?


• What is the “Ring of Fire”?


• Ring of Fire: A zone of frequent earthquakes and volcanic eruptions that encircles the basin of the Pacific Ocean.






• Many tropical Islands like this are created by ocean plates and volcanism.




Ocean Plate

Ocean Plate


Ocean Plate

Ocean Plate


Ocean Plate

Ocean Plate

Volcanic Arch Island Chain / Archipelago

• Video Link! New volcanic island forming– http://www.youtube.com/watch?v=kwETZSARMg

E

http://www.youtube.com/watch?v=kwETZSARMgE

http://www.youtube.com/watch?v=kwETZSARMgE

• Transform-Fault Boundaries: Where two plates are sliding horizontally past one another.


• Coastal California and the Baja Peninsula will become an Island.



• Continental Convergence: (Mountain Building).


• 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.


• Himalayas: Tallest Mountains on Earth.

• Continent Divergence (Moving apart).


• Ocean vs. Ocean Convergence


• Antilles in Caribbean

• Aleutian Islands Alaska

• Indonesia – Every triangle is a volcano

Documents

Plate Tectonics 7 th Grade Science. Area of Focus: Plate Tectonics Copyright © 2010 Ryan P. Murphy