During 29 June-5 July the seismic network at Popocatépetl detected 128-193 daily emissions and as many as five daily explosions. Cloud cover often prevented observations, although crater incandescence was visible every night. Explosions at 1348 and 1405 on 4 July produced ash plumes that rose 1.5 and 1.2 km above the crater, respectively. Ashfall was reported in Atlatlahucan (30 km WSW) and Tepetlixpa (20 km W). 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)