Report on Popocatepetl (Mexico) — September 1999
Bulletin of the Global Volcanism Network, vol. 24, no. 9 (September 1999)
Managing Editor: Richard Wunderman.
Popocatepetl (Mexico) Continued minor seismicity and light ash emissions
Please cite this report as:
Global Volcanism Program, 1999. Report on Popocatepetl (Mexico) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 24:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199909-341090.
19.023°N, 98.622°W; summit elev. 5393 m
All times are local (unless otherwise noted)
Low-level activity continued throughout most of July, August, September, and into the first week of October, with only small-to-moderate exhalations and some light gas and steam emissions. Generally, fumarolic activity was low, but clouds frequently obstructed visibility. The hazard status remained Yellow and the radius of restricted access remained at 5 km. A M 7.4 earthquake in the state of Oaxaca on 30 September did not affect the volcano.
Low-magnitude microseismic and/or tectonic events occurred occasionally. Type-A earthquake events were recorded at the following times: M 2.2 at 0141 on 14 July (preceded by a type-A microseism); M 3.3 at 2053 on 15 July; M 2.1 at 2336 on 23 July (followed by a small tectonic type-A event on 25 July); a small-magnitude event at 1638 on 29 August; and two events at 2008 and 2148 on 1 September of M 2.2 and 2.5, respectively.
Several low-magnitude tectono-volcanic earthquakes were also detected as follows: M 2.7 at 0654 on 28 July; two events at 2029 on 29 July with M 2.0 and 2.6, respectively; a M 2.5 event at 1431 on 6 September at a depth of 7.9 km from the summit and 5 km S of the crater; M 3.2 at 2047 on 8 September with its hypocenter at 7.1 km below the summit and 6 km S of the crater; and another M 3.2 event at 0834 on 27 September at a depth of 5.3 km under the summit and 6 km SSE of the crater.
Moderate exhalations starting in late August continued through September and into the first week of October. At 0920 on 27 August two small ash emissions caused light ashfall over several towns on the W flank. Another emission on 1 September caused minor ashfall. A larger event with a duration of two minutes occurred at 2205 on 5 September, causing light ashfall over several towns. At 0757 on 20 September a small exhalation ejected a plume 1 km above the summit before dispersing to the W. Two moderate exhalations occurred at 0916 and 0949 on 29 September, both lasting about 2 minutes, with ash falling W of the volcano about an hour later.
Volcanic activity during the first week of October, subsequent to a M 7.4 earthquake in the state of Oaxaca on 30 September and a number of aftershocks, remained similar to recent months. At 1101 on 3 October, a moderately large exhalation lasted for more than 15 minutes; the ash column rose to 4 km above the crater and ash fell on several towns to the SW.
Geologic Background. 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.
Information Contacts: Servando De la Cruz-Reyna1, 2, Roberto Quaas1, 2; Carlos Valdés G.2, and Alicia Martinez Bringas1.1-Centro Nacional de Prevencion de Desastres (CENAPRED), Delfin Madrigal 665, Col. Pedregal de Santo Domingo, Coyoacán, 04360, México D.F. (URL: https://www.gob.mx/cenapred/); 2-Instituto de Geofisica, UNAM, Coyoacán 04510, México D.F., México.