Plate Tectonics

By: Austin Chaney period 1

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Earth's Layers

Earth is composed of three layers. These layers are the core, mantle, and crust. The core (or at least inner core) is a solid ball that is around 5400 degrees Celsius. The mantle is between the crust and the outermost part of the core. The mantle composes about 84% of earths volume, and is about 1,800 miles thick, Finally the crust is the shell of the earth. The earth's crust is composed of both oceanic and continental crust. The crust can range from any where between 10-70 km thick. We live and thrive on the earth's crust. Comprehending earth's layers is important because they are very pertinent when talking about plate tectonics. If we can grasp that earth's tectonic plates are driven by the molten lava coming from the mantle, then we can understand why horrendous events like earthquakes are taking place and why the continents are moving apart.

Continental Drift

Continental drift is a theory that was first hypothesized by Alfred Wegener . It encompasses earth's plates movement relative to each other. It Is said that all of the plates were once interlocked, forming a super-continent named Pangaea.

Alfred Wegener

German scientist Alfred Wegener First came up with his theory for continental drift in the early 20th century. Alfred published a book conveying his thoughts on the theory of continental drift. In his book he went on to explain "that the coasts of western Africa and eastern South America looked like the edges of interlocking pieces of a jigsaw puzzle" (continental drift, national geographic education). Although he was not the first to discover this, he was the first to formally present his findings (continental drift, national geographic education).
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Evidence of continental drift

Alfred Wegener noticed that the coasts of western Africa and eastern south America could fit together, like a puzzle. This led him to believe that all the continents could interlock. Also, similar animal and plant fossils were fond on continents that were separated by a colossal ocean (Dive and Discover : History of Oceanography). This also provoked the idea that these continents were once united together.

Sea-floor Spreading

This is a process where new oceanic crust is formed by the rising of magma. The immense pressure of the magma moves the plates apart, and fills the gap creating new land. This creating of land can be seen in many places. The most recently created crust is at the mid-Atlantic ridge, where the actual site of seafloor spreading is (seafloor spreading, national geographic education). Seafloor spreading's astonishing powers can create wonders like bodies of water and large amounts of land. An example of this phenomenon is the red sea (seafloor spreading, national geographic education).

Who discovered seafloor spreading?

Harry Hess was the man responsible for discovering seafloor spreading (PBS). Hess was a geologist and a navy sub commander during world war two (PBS). He was tasked with the mission to delve into the depths of the ocean for research purposes. After discovering sunken islands and the great global rift, he was inspired to look at his research from years before (PBS). With this information, he discovered that it was seafloor spreading that caused the movement of the continents.

Seafloor spreading's relevance in the theory of continental drift

Seafloor spreading is very pertinent in the theory of continental drift in that it goads the separation of the continents by forming new land. The ever-so powerful convection currents break and push apart the land (which could be the 12 major plates) by forcing magma between them. The magma then gets cooled by the seawater and creates new land. This helps explain why the plates have moved apart, and why the appearance of the earth is changing so slowly. it happens so slowly because the process of subduction. Subduction is the polar opposite of seafloor spreading. in this process, the heavier (denser) tectonic plate is sucked underneath the lighter one (less dense), causing the subdued land to be destroyed by the scorching hot magma (seafloor spreading,national geographic education). This process is the counterpart to seafloor spreading, in that it destroys land rather than creating it. This all explains why the plates are moving away from each other, and why they are moving so excruciatingly slow.

How does convection help with plate movement?

Convection is one of the primary ways that plates use to move around. Convection (heat rises cold sinks) causes the magma to rise from the ground, creating a rift between two plates that causes the plates to push away from each other. This movement is entirely created by convection, for its convection's role in the rising of magma that made this possible.

Theory of plate tectonics

the theory of plate tectonics is that the lithosphere is divided into 12 major plates that constantly move away from each other at a very slow pace. This theory has been supported by a multitude of evidence. For example, the process of convection can be shown as a leading factor of plate tectonics. This process creates a space between two plates by putting enough pressure between them to move them away from each other.

Plate boundaries

There is a somewhat large variety of ways plate boundaries can works. One of these ways is a convergent boundary. Essentially, a convergent boundary consists of two plates (whether they be oceanic or continental) colliding with each other. This collision can either occur in one of two ways. Either one plate will be subdued under the other (only when oceanic and continental collide) causing convergent subduction which usually generates trenches and other landforms alike. The other path convergent boundaries can take is convergent continents. This will usually create mountains and such. Next is divergent boundaries. Divergent boundaries are boundaries where instead of colliding, the plates move apart and diverge from each other. Divergent boundaries will either occur in the ocean or on land (continents). The last form of boundaries is the transform boundary. Transform boundaries cause the plates to slide past each other, causing catastrophic earthquakes.
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The ring of fire

The ring of fire is a very significant geographic phenomenon. This string of volcanoes encompassing the outer edge of the pacific coast contains 75 percent of all active volcanoes in the world. Also, 90 percent of all earthquakes occur here. The ring of fire is located primarily on boundaries, so it is very relevant in the field of plate tectonics.
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Geographic features

Along with tectonic boundaries comes landforms and disasters. At convergent (no subduction) boundaries mountains tend to form. At convergent boundaries with subduction, trenches and volcanic mountain ranges usually form. At divergent boundaries, the process of sea-floor spreading occurs. At transform boundaries, earthquakes happen.
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