Transcript plate tectonics

Plate Tectonics
How can continents move?
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In the 1960’s, scientists aboard the research
ship Glomar Challenger drilled into the
seafloor of the Atlantic Ocean and removed
crust samples.
None of the rock samples were over 200
million years old. (Samples of continents
are over 3 billion years old)
Rocks at the mid-ocean ridges were
younger; rocks became older in both
directions closer to the continents.
Glomar Challenger
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After analyzing the rock samples, scientists came
up with a theory that molten material from Earth’s
mantle is forced upward to the surface at midocean ridges and cools to form new sea floor.
Movement in Earth’s mantle forces sections of
crust apart, allowing magma to flow onto Earth’s
surface and form new crust.
Therefore, the Atlantic Ocean is wider today than
it was when Christopher Columbus crossed it!!!
Plate Tectonics- theory that
Earth’s crust and upper mantle
(lithoshphere) are broken into
sections called plates that move
on top of the asthenosphere.
Types of Plate Boundaries
Convergent-plates collide
Divergent-plates separate
Transform-plates slide past each other
Plate Map
Converging Plates
Divergent Plates
Transform Plates
Convection Currents
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Scientists believe plate movement is caused
by convection currents.
When material in the mantle reaches an
extreme high temperature, it rises. When it
cools, it begins to sink back down. This
motion creates a current, like when soup
boils.
Convection currents
Convection currents
Convergent Boundaries
Oceanic/Continental
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Andes Mts (S. America)
South American & Nazca Plates
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Cascade Mts, Mt.St. Helens (N. America)
North American & Juan de Fuca Plates
Effects of oceanic/continental
convergence
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Volcanic mountain
chains
Faults
Earthquakes
Click picture for
short video
Ocean/Continent Convergence
Andes Mountains
Mount St. Helens
Convergent Boundaries Con’t
Oceanic/Oceanic
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Japan Island chain
Eurasian & Pacific Plates
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Philippine Islands
Eurasian & Pacific Plates
Effects of oceanic/oceanic
convergence
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Volcanic island arc
Faults
Earthquakes
Tsunamis
Ocean/Ocean Convergence
Mt. Pinatubo, Philiippines
Mt. Fugi, Japan
Convergent Plates Continued
Continental/Continental
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Appalachian & Atlas Mts.
African & N. American Plates
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Himalayas
Indian & Eurasian Plates
Effects of continental/continental
convergence
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Folded mountain
ranges
Faults
Earthquakes
Click pic for short
video
Continent/continent convergence
Himalayas
Divergent Plate Boundaries
Oceanic Crust
Mid Atlantic Ridge (MAR) and Iceland
N. American & Eurasian plates
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Effects:
 Mid ocean ridges
 Faults
 Earthquakes
 volcanos
Computer generation of MAR
Mid Atlantic Ridge
Iceland
Continental crust divergence
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East Africa, Red
Sea & Rift Valley
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Effects:
Rift valleys
Faults
Earthquakes
Inland seas
Rare volcanos
Red Sea
Transform Plate Boundaries
Continental & Oceanic Plates
San Andreas Fault (California)
Pacific & N. American Plates
Effects:
 Faults
 Volcanos
Click for
short video
Transform Boundary
San Andreas Lake
San Andreas trench
Hot Spots
Areas of volcanic activity formed by areas of
intense heat in the mantle at places other than
plate boundaries
Ex: Hawaiian Islands, Yellowstone Natl. Park
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Click for
short video
Hawaiian Islands
Cross section of hot spot