Plate Tectonics By: Ali chmielewski and Maddie fitzgerald

Plat Tectonics Theory: the lithosphere of the earth is divided into a small number of plates which float on and travel independently over the mantle and much of the earth's seismic activity occurs at the boundaries of these plates.

Plate Tectonics is a theory of global tectonics in which the lithosphere is divided into a number of crustal plates, each of which moves on the asthenosphere. Continental Drift, however, is a theory developed by Alfred Wager who suggested that in the past, there was a super continent called Pangaea.

The continents have moved a great deal in the history of the planet, but they carry records of where they’ve been. Some of this evidence is the fossils of animals and plants. Tropical species found in the Antarctic and similar fossils found in western Africa and eastern South America tell a story of where those land masses used to be. Paleomagnetic evidence is an even stronger piece of evidence. Magnetic strata within the fossil record show how the land masses were oriented at different times during Earth’s history. By constructing detailed records of changes in land mass orientation, scientists can reconstruct paths of tectonic movement much further back in history than they can from the magnetic striping on the sea floor.

The basic theory of plate tectonics is that along seafloor spreading zones, the continents are separating from one another. As they spread apart, magma comes to the surface and becomes new continental crust. As the tectonic plates move away from spreading zones, they collide with one another.


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