As little as a hundred years ago, earthquakes were thought to be spawned by demons or deities. The mere thought that something as solid and obviously stationary as the ground we stood on could actually be moving was considered ludicrous.

It had been noticed by the late 1500's that certain landmasses such as Africa and South America seemed to fit together, yet despite this, scientists believed that the landmasses were stationary.

In the late 19th century, the presence of radioactive elements was discovered in the crust, and the heating abilities of the elements caused a shift in thinking. Using the new information, in 1912, Alfred Wegener put forth a new theory, the one called Continental Drift.

Continental drift suggests that at some time in the past, all the continents and landmasses were together, forming one giant super continent. As time went by, the giant continent broke up and the pieces floated away from each other. The mechanism for this, other that saying that it was because of the heat released by radioactivity was not explained. As a consequence, few scientists took the theory seriously.

The first supporting evidence for the theory of continental drift came from early seismology. When earthquake waves move through solid rock, they do so at a relatively constant rate. But when they encounter rock that is elastic rather than solid, each of the waves slows down and lessens in intensity since the elastic rock can give under the pressure.

From this information, scientists were able to deduce that not only was the rock under the crust in a semi-fluid state, but that there were areas where this elastic rock approached the surface or actually broke through to the surface. The bands where this happens occur mostly in the ocean, particularly in a ring located around the Pacific basin, which is called the Ring of Fire, since this is also an area that is very active volcanically.

In the last fifty years, the theory of continental drift has evolved into Plate Tectonics, as more information has been learned. It has been found that there are three main kinds of boundaries between the tectonic plates.

In constructive plate boundaries, the plates are pulling away from each other, allowing magma to rise to the surface from the mantle to create new rock. An example of this occurs roughly in the middle of the Atlantic Ocean and includes Iceland, where geologists can actually study the phenomenon.

In destructive plate boundaries, plates move

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