What Is the Theory of Plate Tectonics

Edited by TPappin, Sharingknowledge, Jen Moreau

What is Plate Tectonics?

Plate tectonics is a theory that was first proposed in the early 1900s by scientist Alfred Wegener, but was not said to be true until the 1960s.

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    What It States
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    It states that Earth's outer shell is made up of many different plates, all which glide over top the Earth's mantle. The plates are found in the lithosphere. Also known as continental drift, the theory of plate tectonics is the reasoning behind why and how continents are constantly moving.
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    Why It Occurs
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    The movement of continents is caused by what's happening beneath Earth's crust. Seismic waves, which are waves of energy that occur when tectonic plates push against each other and pull apart, cause rock within the Earth to suddenly break, causing disruption and in some cases, even explosion or volcanoes. Seismologist Nicolas Van der Elst describes the process as "…a pot boiling on a stove."
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The History of Plate Tectonics

When Alfred Wegener first proposed the theory of continental drift, he described the tectonic plates, or the continents, as puzzle pieces fitting together. He continued to explain his theory after realizing the Earth's surface changing significantly over time while noticing that continents which, at one point, were not separated, were. This was also noted by paleontologists when fossils of the same species were found on different continents, now separated. Their combined observations determined that the Earth's lithosphere had, in fact, been moving over time.

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    Controversy
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    Not everyone agreed with Wegener's theory, as there wasn't really a way to prove why the continents were moving, other than his observation. Many other scientists believed it was due to the Earth's temperatures, causing continents to contract.
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    Disproved
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    Wegener originally proposed that Earth's continents pushed against the ocean floors, although he was unable to identify the direct cause of continental drift. For that reason, geologists deemed his theory false; however, it did lay the groundwork for the development of plate tectonics and over time, additional evidence was gathered.
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    Seismometers
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    After World War II, several seismometers were installed all over the world, in order to monitor nuclear testing. This is what ultimately lead to the discovery of tectonic plates. Their findings showed that earthquakes and volcanoes formed along the edges of tectonic plates.
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    1960s
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    In the 1960s is when the plate tectonic theory started to gain acceptance across the world.
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The Plates

The tectonic plates are found in the Earth's lithosphere, which is the outermost shell, or in other words, the crust and the mantle combined. The lithosphere is broken up into seven or eight major tectonic plates, as well as several minor ones.

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    Their Names
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    Each of the major tectonic plates has their own unique name: African plate, Antarctic plate, Eurasian plate, Indo-Australian plate, North American plate, Pacific plate and South American plate. These plates account for 94% of the Earth's surface.
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    What They Do
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    The tectonic plates are constantly in motion, which is what ultimately starts earthquakes, volcanoes, mountain formations and oceanic trenches. Each plate is about 80 km deep and moves only a few inches each year.
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Plate Boundaries

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    What They Are
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    Plate boundaries are where each of the tectonic plates meet. There are three main types of plate boundaries, also known as subduction zones or convergent margins: convergent boundaries, divergent boundaries and transform boundaries.
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    Convergent Boundaries
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    When two plates meet underwater and one or both are composed of oceanic crust. The plate which is denser is pushed underneath the less dense tectonic plate, which eventually melts and is destroyed completely.
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    Divergent Boundaries
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    Divergent boundaries are when two tectonic plates are moving away from one another. This process can occur underwater or on land.
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    Transform Boundaries
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    Transform boundaries are when two tectonic plates slide horizontally past one another. Like divergent boundaries, transform boundaries can occur underwater or on land. When the two plates slide past each other, friction is caused, building up stress in both plates, which then causes an earthquake. This is also known as a fault, or a fault plane.
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Plate Collisions

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    What Is It
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    Plate collisions occur when the subduction zone between two plates is destroyed. It is a phenomenon of the plate tectonics. When this happens, mountains can be formed, volcanoes can erupt and two continents ultimately come together, affecting what the map of the Earth looks like.
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    The Himalayas
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    The Himalayan Mountain formed as a result of the Indian Plate and Eurasian Plate colliding. This process began 50 million years ago and continues to this day. The continental crust of both plates buckled, causing rock to pile up.
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    When Oceanic and Continental Plates Collide
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    Continental crust is typically thinner than oceanic crust, which means when the two collide, the oceanic crust ultimately gets pulled beneath the lighter and thicker continental crust. This process forms a subduction zone.
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    Subduction Zones
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    All subduction zones must eventually disappear. Once they do, the tectonic plates will collide, creating a mountain range. This has already occurred a number of times across the world.
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    The Wilson Cycle
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    The Wilson Cycle refers to the recurrent opening and closing of ocean basins, causing the Earth to move. It starts when magma erupts toward the Earth's crust, forming an ocean basis, acting as a final resting spot for the settled magma.
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What Is the Theory of Plate Tectonics. (2017). In ScienceAid. Retrieved Jul 22, 2018, from https://scienceaid.net/What_Is_the_Theory_of_Plate_Tectonics

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Categories : Geology

Recent edits by: Sharingknowledge, TPappin

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