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The mantle is made of two layers, the lithosphere and the asthenosphere. The asthenosphere moves the crust around causing the plate tectonic theory. It does this by convection currents, which are caused by the heat from core and the lower mantle. The hotter material would rise up as the somewhat cooler material would sink to the core and heat up again. This is important to the plate tectonic theory because the plates that make up the crust are always slowly moving.

Continental Drift was theorized by the German scientist, Alfred Wegner. Continental Drift is the theory that all the continents used to be part of one supercontinent and slowly moved apart. The four main pieces of evidence that he used were fossils Gossopteris and Mesosaurus; other scientists were very doubtful of this because some of the evidence he presented were pushed off as a coincidence. Other evidence were that the boundaries of South America and Africa fit together, and the last piece was coal and glacier deposits in places that were not possible.

Sea-floor spreading was a theory proposed by Harry Hess. The theory stated that the ocean areas where magma would push out and push the ocean floor away and creates new oceanic crust. Three pieces that Hess used to prove this theory were the molten material near the mid ocean ridge, magnetic stripes, and drilling samples from sides of the ridge. This theory is important because it completed the missing piece of Alfred Wegner's Continental Drift.

There are 3 different types of stress that the tectonic plates have, compression, tension, and shearing. Stress is a force that adds potential energy to the lithosphere until it changes shape or breaks or moves. Compression is the motion of the plates compressing against each other. Tension is the motion of the plates pulling away in opposite directions. Shearing is when the plates grind past each other.

The theory of Plate Tectonics explains the formation, movement, and subduction of Earth's Plates. The things that cause this is stress, a force that adds potential energy to the lithosphere until something happens. There are three types of stress compression, which means plates colliding against each other, tension, which is the plates moving away from each other, and shearing, which means that the plates are sliding past each other.

Convergent boundaries are plates that are pushing towards each other. They move because the lithosphere is underneath using convection currents. The oceanic plate would go under the continental plate creating a subduction zone. This action usually causes the creation of mountains, trenches, volcanoes, and island arcs.