CENAPRED reported that during 12-18 September seismicity at Popocatépetl indicated continuing gas-and-steam emissions that sometimes contained ash; cloud cover often prevented visual observations of the volcano. Incandescence from the crater was observed most nights. On 13 September gas-and-steam plumes rose 2 km above the crater and drifted NE. Later that day a gas-and-ash plume rose 2 km. Incandescent tephra was ejected 500 m and fell on the NE flanks. On 14 September incandescent tephra fell on the N flank and gas-and-ash plumes rose 1 km. The next day gas-and-ash plumes again rose 1 km. During 16-18 September gas plumes continued to rise 1 km at most and drifted NE, NW, and SW. The Alert Level remained at Yellow, Phase Two.

Geological Summary. Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Source: Centro Nacional de Prevencion de Desastres (CENAPRED)