Theory of Tectonic Plates
Cole Bahan
3.1.2014
7th Hour
Mrs. Martin
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What Tectonic Plate
Plate tectonics is the theory that the outer rigid layer of the earth the lithosphere is
divided into a few dozen “plates” that flow around the earth’s surface. These plates are called
tectonic plates or lithospheric plates. They are slabs of rock on the lithosphere that move across
the area and span a few hundred to thousands kilometers across. There are 3 types of tectonic
plates. The plates can be continental, oceanic or both. The plates can be pushed around by
convection currents in the asthenosphere. These plates are divided up into primary and secondary
groups.
Secondary and Primary Tectonic Plates
There are a total of 15 primary and secondary plates. These plates are the one you will
see on most big tectonic plate maps. There are 7 different primary plates. These plates make up
most of the continents and Pacific Ocean. The plates are the African Plate, Antarctic Plate,
Eurasian Plate, Indo-Australian Plate, North American Plate, Pacific Plate, and the South
American Plate. Secondary plates are smaller plates than the primary but just as well know.
There are 8 different secondary plates. These secondary plates that make the rest of the earth’s
surface. The Plates are Arabian Plate, Caribbean Plate, Cocos Plate, Indian Plate, Juan de Fuca
Plate, Nazca Plate, Philippine Sea Plate, and the Scotia Plate. These plates are not shown on most
maps except the Indian plate and the Arabian Plate.
Tertiary Plates
We do not here much about these plates because they are grouped with the major plates
on major plate maps. There is no agreement on how many tertiary plates there are but scattered
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around scientists have identified 58 of them to date. They are sub plates of primary and
secondary plates. These are mostly micro plates that were once part of a bigger plate and broke
off. Most of the tertiary plates are from ancient plates that roamed the earth millions of years
ago. The plates can cause earthquakes and tsunamis just like any other plate.
Plate Movement
Plates move along plate boundaries. The plates can move in three different directions.
They can move together, apart from each other, and parallel to each other. When moving the can
cause earthquakes and tsunamis. They also change the geological features of the earth by
creating mountains and valleys. When plates move away from each other it is called divergent
movement. This can create rift valleys and volcanic islands. This happens when molten lava
from underneath the sea rise from opening in the plate boundaries. When plates start to move
towards each other it is called convergent movement. The plates collide and can make
earthquakes and mountains. Some examples are the Indian Plate and the Eurasian plate forming
the Himalayas. When the plates collide one can get sucked under the other plate and is called a
seductive plate. Convergent and divergent plates can also make volcanos and trenches. Plates
moving parallel to each other are called adjacent plates. Sometimes adjacent plates move along
their boundaries which is called a strike-slip fault. Although movement along the fault lines does
not create Mountains or valleys is does create a lot of earthquakes.
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Work Cited
"How Many Tectonic Plates Are There?" WiseGEEK. N.p., n.d. Web. 01 Mar. 2014.
Oskin, Becky. "What Is Plate Tectonics?" LiveScience. TechMedia Network, 23 June 2013. Web. 01
Mar. 2014.
"An Updated Digital Model of Plate Boundaries: PB2002." An Updated Digital Model of Plate
Boundaries: PB2002. N.p., n.d. Web. 03 Mar. 2014.
"What Is a Tectonic Plate? [This Dynamic Earth, USGS]." What Is a Tectonic Plate? [This Dynamic
Earth, USGS]. N.p., n.d. Web. 03 Mar. 2014.
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