CENAPRED reported that eruptive activity continued at Popocatépetl during 5-11 July. Long-period events totaling 25-123 per day were accompanied by steam-and-gas plumes that sometimes contained minor amounts of ash. Seismic activity also included variable-amplitude volcanic tremors (total of 35 hours), harmonic tremor (9.5 hours), explosions, and volcano-tectonic earthquakes (maximum magnitude 1.6 at 0441 on 9 July). Ash plumes identified in webcam and satellite images were described in daily aviation notices issued by the Washington VAAC; some plumes rose as high as 2.2 km above the summit and drifted NE, SW, W, or NW. Minor explosions occurred at 2336 on 4 July, at 1955 on 6 July, at 0911 and 1937 on 7 July, at 1016 on 8 July, and at 0209 and 0335 on 11 July. Moderate explosions were recorded at 0007 on 9 July and at 0816 on 11 July. At 0843 on 10 July the VAAC reported an ash plume that rose 1 km above the summit and drifted as far as 28 km NW. At 0930 on 10 July ashfall was reported in the municipalities of Ayapango (24 km WNW), Tenango del Aire (29 km WNW), Amecameca (19 km NW), and Temamatla (33 km NW), all within the State of México. The VAAC reported that the plume drifted as far as 185 km NW by noon, and the Secretaría de Gestión Integral de Riesgos y Protección Civil (SGIRPC) of the City of México reported ashfall in Milpa Alta (46 km WNW), Xochimilco (56 km WNW), Coyoacán (65 km WNW), Tlalpan (67 km WNW), La Magdalena Contreras (70 km WNW), Álvaro Obregón (72 km WNW), Cuajimalpa (80 km WNW), Tláhuac (49 km NW), and Iztapalapa (59 km NW). On the morning of 11 July ashfall was reported in the municipalities of Ozumba (18 km W) and Juchitepec (30 km WNW) within the State of México. 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), Secretaría de Gestión Integral de Riesgos y Protección Civil (SGIRPC)