CENAPRED reported that there were 27-62 steam-and-gas emissions, sometimes containing minor amounts of ash, rising from Popocatépetl each day during 19-25 October. Weather clouds often prevented visual observations of activity. The seismic network recorded daily periods of tremor lasting from 16 minutes to 10 hours and 35 minutes. One or two daily volcano-tectonic earthquakes were recorded. During 20-23 October daily periods of low-amplitude, high-frequency events varied between two hours and 19 minutes to five hours, and periods of harmonic tremor lasted from 11 minutes to five hours and 35 minutes. A small explosion was recorded at 0039 on 25 October. According to a news article a small new lava dome, about 60 m in diameter, had been growing on the crater floor since 7 October. The Alert Level remained at Yellow, Phase Two (the middle level on a three-color scale).

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), Tribuna Noticias