Report on Popocatepetl (Mexico) — January 1999
Bulletin of the Global Volcanism Network, vol. 24, no. 1 (January 1999)
Managing Editor: Richard Wunderman.
Popocatepetl (Mexico) Intermittent gas-and-ash plumes during 18-29 January
Please cite this report as:
Global Volcanism Program, 1999. Report on Popocatepetl (Mexico) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 24:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199901-341090.
19.023°N, 98.622°W; summit elev. 5393 m
All times are local (unless otherwise noted)
Activity at Popocatépetl during January was generally stable, characterized by periodic low-level, short-duration exhalations and high-frequency tremor. Restrictions on access closer than 7 km to the crater continued. The traffic-light alert signal remained Yellow.
Volcano-tectonic A-type earthquakes occurred at: 1302 and 2327 on 1 January; 0126, 0550, and 0745 on 9 January; 0152 on 10 January; and 2353 on 14 January. Twelve minutes of tremor began at 1127 on 10 January and 40 minutes of tremor were recorded on 20 January beginning at 0634. Several moderately large exhalations of steam and gas were noted during the month including those on 4, 9, 10, and 15 January. A small ash puff rose 500 m above the summit on 18 January before dispersing to the SW. Emissions of steam, gas, and ash were accompanied by episodes of tremor on 20, 21, and 26 January.
Low-amplitude, high-frequency tremor was detected beginning at 1306 on 27 January. The public warning against approaching closer to the crater than 7 km was reemphasized. An increase in the amplitude of the tremor signal began at 1341. The increase was accompanied by a plume of steam, gas, and ash that rose 3 km above the summit. Prevailing winds carried the ash toward the NE where minor ashfalls were expected. Activity returned to previous lower levels early in the evening. A similar episode occurred on 29 January. Fifteen minutes of tremor began at 1254 accompanied by a steam-gas-and-ash plume that rose 3 km above the summit before being blown to the NE. More moderate activity returned later in the day.
In response to some possibly incorrect information contained in a local news broadcast on 14 January, CENAPRED outlined changes to the crater as observed by scientists on the volcano. No significant changes have been observed since the explosive activity of 17 December 1998 (BGVN 23:12). That explosion removed a moderate amount of lava from an inner craterlet on the dome inside the main crater. This inner craterlet was ~300 m in diameter before 17 December and, after the explosion, it had a depth (relative to the dome) of ~75 m. These dimensions are nearly identical to those it had in October 1998. The shape, conditions, and general activity within the main crater are similar to those in October.
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.