The earthquake is the largest one since the deadly 19-85 quake that killed some 5,000 people. Mexico lies on the circum-Pacific belt, a seismic zone so volatile that it's nicknamed the "Ring of Fire". There are 452 volcanoes altogether on the belt -- that's 75 percent of the world's active AND dormant ones. About 90 percent of the world's earthquakes and 81 percent of the world's LARGEST earthquakes occur along the Ring of Fire. The other two large seismic zones are the Alpine-Himalayan and Mid-Ocean Ridge belts.