Centro Nacional de Prevención de Desastres (CENAPRED) reported that eruptive activity continued at Popocatépetl during 16-22 October. The seismic network recorded 9-89 long-period events per day that were accompanied by steam-and-gas emissions. The seismic network also recorded daily tremor with periods lasting from 54 minutes up to 13 hours and 17 minutes, and a period of emissions that lasted 35 minutes during 15-16 October. Two volcano-tectonic earthquakes were recorded during 0100-0200 on 16 October. A single volcano-tectonic earthquake was detected at 1639 on 20 October. A significant tremor episode that began at 1147 was accompanied by a gas-and-ash plume that rose 2 km above the crater and incandescent material that was ejected a short distance from the crater. Based on information from El Centro Nacional de Comunicación y Operación de Protección Civil (CENACOM) ashfall was reported in Ozumba (18 km W), Tlalmanalco (30 km NW), and Ecatzingo (15 km SW) in the state of Mexico; and around 0958 in Tlalnepantla (80 km NW), Tlayacapan (40 km WSW), and Totolapan in the state of Morelos.

According to the Washington VAAC ash plumes visible in webcam and satellite images during 17-21 October rose to 5.8-7.3 km (19,000-24,000 ft) a.s.l. and drifted in different directions. The Alert Level remained at Yellow, Phase Two (the middle level on a three-color scale) and the public was warned to stay 12 km away from the crater.

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.

Sources: Centro Nacional de Prevencion de Desastres (CENAPRED), Washington Volcanic Ash Advisory Center (VAAC)