CENAPRED reported that eruptive activity continued at Popocatépetl during 19-26 September. Long-period events totaling 151-640 per day were accompanied by steam-and-gas plumes that sometimes contained minor amounts of ash. Periods of volcanic tremor were recorded almost daily, often characterized as low-amplitude and high-frequency, and each lasted 37-297 minutes. One to two volcano-tectonic earthquakes per day were recorded during 19-22 September and had magnitudes of 1.4-2.5. A moderate explosion was recorded at 1305 on 21 September and a minor one was recorded later that day at 1704. A minor explosion occurred at 0907 on 22 September. During the morning of 24 September ash plumes drifted over the municipalities of Yautepec (50 km WSW), Cuautla (43 km SW), Ayala (45 km SW), and Yecapixtla (31 km SW), and possibly Tlaltizapán and Tlaquiltenango in the state of Morelos. Minor ashfall was reported in the municipalities of Tetela del Volcán (20 km SW) and Tepalcingo during the morning of 25 September and in Villa de Ayala later that day; the municipalities were in the state of Morelos. 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.

Source: Centro Nacional de Prevencion de Desastres (CENAPRED)