CENAPRED reported that there were 81-238 steam-and-gas emissions, often containing ash, rising from Popocatépetl each day during 24-31 January and explosions occurred almost daily. Two explosions were recorded at 1424 and 1426 on 24 January. Minor ashfall was reported on 25 January in San Nicolás de los Ranchos (15 km ENE). Later that day, at 2231, an explosion ejected incandescent material onto the flanks. An overflight was conducted by Instituto de Geofísica de la Universidad Nacional Autónoma de México (UNAM) and the Guardia Nacional on 27 January to observe the crater. They saw a small lava dome that was about 30-40 m in diameter and 5-10 m tall on the inner crater floor. The inner crater floor had remnants of the previous domes mixed with fine tephra deposits and was 160-180 m deep. The rim of the inner crater was 390-410 m in diameter, similar to previous observations. A minor explosion later that day at 2214 produced an ash plume, based on a webcam image. Minor explosions were recorded at 0451, 0521, 1828, and 2232 on 28 January. A webcam image from 0343 on 29 January showed deposits of incandescent material that was ejected onto the flanks. Another explosion occurred at 2254. Explosions were noted at 0141 and 0621 on 30 January; minor ashfall was recorded in Amecameca (19 km NW), Temamatla (32 km NW), and Tenango Del Aire (28 km NW). A moderate explosion at 0029 on 31 January produced an ash plume that rose 1.8 km above the crater rim and ejected incandescent material onto the flanks almost 2 km from the crater rim. Minor explosions occurred at 0533, 0619, and 0721. 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.

Source: Centro Nacional de Prevencion de Desastres (CENAPRED)