Plate Tectonics Review
Continental Drift- The theory that the continents were once connected in a super
continent called Pangaea and have since drifted apart.
This theory was proposed by Alfred Wegner and he used the following pieces of
evidence to support his theory:
#1- The continents appear to fit together like a puzzle
#2- The presence of coal deposits in countries now separated
#3- Matching rock strata in countries now separated
#4- Fossils of tropical plants found in the Arctic
#5 Glacial markings
**This theory later developed into the theory of Plate Tectonics when
technology allowed scientists to see evidence of sea floor spreading,
rift valleys, and ocean ridges***
Plate Movement:
Earth's plates "float" on the asthenosphere (the upper part of the mantle).
Convection in the mantle causes the plates to move. When the warm magma
rises pushing the plates apart and the cool magma sinks pulling plates down.
**REMEMBER CONTINENTAL CRUST IS THICKER BUT LESS DENSE,
OCEANIC CRUST IS THINNER BUT MORE DENSE**
Convergence: (Come Together)
-These are plates that are moving TOWARD each other
-They are called destructive boundaries because part of the plate is being
destroyed as they come together
http://www.utexas.edu/tmm/npl/mineralogy/mineral_genesis/
WHEN 2 CONTINENTAL PLATES CONVERGE IT MAKES MOUNTAINS
WHEN AN OCEAN AND CONTINENTAL PLATE CONVERGE IT MAKES
VOLCANOES
www.nature.nps.gov
WHEN TWO OCEANIC PLATES CONVERGE IT MAKES A TRENCH
Divergence (Divide):
-Diverging plates move AWAY from each other
-These are called CONSTRUCTIVE boundaries because new crust is being created
-When two continental plates diverge it creates rift valleys
http://www.moorlandschool.co.uk/earth/tectonic.htm
-When two oceanic plates diverge it creates mid ocean ridges (we call this sea floor
spreading)
http://mail.colonial.net/~hkaiter/platetectonics.html
Hot Spots
Hot spots occur where the crust is thin. This is how the Hawaiian Islands were
formed. The island FARTHEST from the hot spot is the oldest)
http://www.whoi.edu/oceanus/v2/article/images.do?id=2541
Faults- boundaries where plates are sliding past each other causing
earthquakes. An example of this is the San Andreas Fault.