The Earth is continuously recycling its crust, producing new crust at some late boundaries while destroying old crust at other plate boundaries. All of these locations have a common feature: earthquakes. This is the result of the stress created by the edges of the plates trying to move against each other. Rock can bear a certain amount of strain, but if there is too much, it will eventually break. When such a break occurs, there is movement along the fault, resulting in an earthquake. The geographic location where the break takes place is called the epicenter of the earthquake.

Many earthquakes are minor and do not have much effect at the surface, but the damaging results of a major earthquake can be felt thousands of kilometers from the epicenter.

Click on this globe to spin it around and to show the epicenters of nearly 2000 earthquakes that have been mapped from 1999 to 2003.

This map of earthquake epicenters around the world shows a very close correlation with the location of plate boundaries. Courtesy USGS

The plate tectonic theory helps to explain the geologic differences between the ocean floor and the continents. Young crust is being created in the middle of the ocean floor along the mid-oceanic ridges, but this is not happening on the continents.

This map shows the boundaries of the plates. How does it compare to the map of earthquake epicenters above? Courtesy USGS