Located about 70 km (40 miles) southeast of Mexico City, Popocatépetl is one of Mexico’s most active volcanoes. Popocatépetl has been erupting since January 2005, with near constant venting from fumaroles punctuated by minor steam, gas, and ash emissions.

Activity began to pick up significantly in mid-April. The volcano began emitting a substantial amount of ash on April 12, 2012, and an explosion on April 13 sent volcanic blocks as far as 500 meters (1,640 feet) away from the crater rim. On April 15, an ash plume rose 1.5 kilometers (0.9 miles feet) above the crater.

The last major eruption of Popocatépetl occurred in 800 A.D., in which vast amounts of lava and ash from the volcano completely filled many of the surrounding valleys. Since then, there have been at least five moderate eruptions, two of which occurred in the 1900s.