Massive plates fit together like puzzle pieces deep beneath the Earth. When a plate shifts along one of the fault lines that join them, a violent upheaval takes place on the planet's surface, experienced by us as an earthquake. Countries as far flung as Iran, Chile, Japan and New Zealand are particularly vulnerable to this seismic activity.

The heat map below, based on data compiled by the U.S. NOAA National Geophysical Data Center, includes all earthquakes measuring 6.0 or greater on the Richter scale over the past 40 years. Darker, redder areas indicate a higher frequency of earthquakes and largely mirror the fault lines between the plates below.