Beginning of Essay
is the theory that the positions of the earth's continents have changed a lot through geologic time. The German meteorologist Alfred Wegener proposed the first comprehensive theory of in 1912, on the basis of the way the continents fit together on the opposing ....

Middle of Essay
.... evolved from and replaced Wegener's original thesis. Plate Tectonics is the theory that deals with the structure, history, and dynamics of the earth's crust. The earth's crust is formed of 13 continental plates. The boundaries of the zones are where tectonic activities occur, and where earthquakes and volcanic eruptions tend to happen. The plate tectonics theory was thought up in the 1960s and 1970s, with ideas taken from Wegener’s earlier thoughts. Earlier, Wegener and other scientists had noted that continental crust grows by additions and that a ridge in the middle of the ocean runs almost all the way around the world. It was also noted that ....