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20 Cards in this Set

  • Front
  • Back
The theory of plate tectonics combines what two formally adversary theories
Continental drift and seafloor spreading.
the theory of plate tectonics suggests that the external surface of earth is composed of
12 plate tectonics on which the continents rest.
the plates float on the _______ layer. and cause geological events where?
Asthenosphere; at the plate borders.
The theory of Pangea is the theory that
there was once a supercontinent called pangea and they broke up and moved to their current locations
What evidence was used to produce the theory of continental drift?
puzzle piece fit

occurance of fossils

occurance of geologic landmarks
What is the theory of seafloor spreading?
The idea that the continents are pushed apart as new sea floor is produced along a midocean ridge and pushes out the older sea floor.
What is the source of energy for seafloor spreading?
The convection in the mantle
what evidence was used for the seafloor spreading theory?
seafloor characteristics

Paleomagnetic pattern- change in magnetic field in aging rocks.


Geophysics- distribution of earthquakes and volcanoes.
if ocean floor is being produced at the midocean ridges, where is sea floor being "destroyed"?
deep ocean trenches.
Plate tectonics are always moving. There are three types of boundaries that are classified by their movement next to eachother. What are the three?
1.) Divergent boundaries
2.) Convergent boundaries
3.) shear boundaries
What are the two kinds of crust and what rock do they produce?
Continental Crust- granite (less dense, thicker)

Oceanic Crust- basalt (more dense, thinner, darker)
2 examples of divergent boundaries

East African Rift Zone

Mid ocean ridge
3 examples of convergent boundaries

Himalayan mountains

Deep sea trench

Deep sea trench
2 examples of Shear boundaries

What are the characteristics of older crust?
Further out from the mid ocean ridge

Less bouyant
What is the result of a convergent boundary in each of the following:


Island arcs

volcanic mountains.
what plate boundary and plates caused the islands of Japan? the mariana trench
ocean ocean convergence.
There are two classes of shear boundaries. What are they?
Transform fault-plates moving in opposite direction (San Andreas)

Fracture zone- plates moving in the same direction.
What are hot spots? what did it create?
A stationary source of volcanic activity. As the plate tectonic moves, it creates a chain of islands.

What happens to aging volcanic rock from these hot spots?
They begin to sink and coral reefs grow right where they begin to sink (ATOLL)