These zones
can converge in three ways. Oceanic to continental, Oceanic to Oceanic, and
Continental to continental. Some examples of Convergent Zones take place in the Nazca Plate where it crashes into South American plate to form the Andes
Mountains. The Pacific Plate which crashes into the North American plate, and
the Australian-Indian Plate which also slams into the Eurasian Plate to form the
Himalayas. Another type is the Transform Fault Boundaries. This type occurs when
plates grind past each other. An example of a Transform fault would be the San
Andreas Fault in California. However this can also take place in the ocean. An
example of this would be where the Antarctic plate is grinding past the African
plate. There are three main reasons why the theory of plate tectonics is
supported. A link between plate boundaries and earthquakes show that the
earthquakes occur with in subduction zones rather than in the mantel therefore
providing a way to track a plate decent. Secondly, the ages and thickness of
sediments from ocean floor give scientist an out look of how rocks submerged
giving them a rough estimate of how long plate tectonics has been taking place.
Finally, Island chains that were created by hot spots can provide evidence on
the directions that the plates are moving.
There was still the question on what
was the driving force for the plate’s movements. Several models where proposed
to the scientific community. “The convection current hypothesis stated that
convection cells in the mantel carried plates like a conveyor belt.” (1) The
slab-pull hypothesis stated that “when cold, dense oceanic material is subducted
it pulls the trailing lithosphere along. The Slab-push may occur when gravity
sets the elevated slabs astride the ridge crest in motion.”(1) Pag.505) The
final model encouraged that hot plumes or rock in the mantel created movement
with in the plates. Plate Tectonics have opened a new perspective of geologic
time. It was not know until recently how old Earth was, which is now known to be
4.6 billion years old. This means that in Geologic time humans have only been
here for a fraction of earth’s existence. The theory of Plate Tectonics has
brought all fields of science including chemistry, biology, geology and
paleontology together. This broad base of knowledge can now be used in future
research to unlock the mysteries of earth.
Bibliography
: 1. Tarbuck, Edward J., and Frederick K. Lutgens. Earth: An Introduction to
Physical Geology. New Jersey: Prentice Hall, 1999. 2. Tectonic Designs,
www.platetectonics.com, accessed 10/15/00.
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