Report on Popocatepetl (Mexico) — April 1997
Bulletin of the Global Volcanism Network, vol. 22, no. 4 (April 1997)
Managing Editor: Richard Wunderman.
Popocatepetl (Mexico) Ash ejections send ash above 4 km altitude and cause ashfalls
Please cite this report as:
Global Volcanism Program, 1997. Report on Popocatepetl (Mexico) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 22:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199704-341090.
19.023°N, 98.622°W; summit elev. 5393 m
All times are local (unless otherwise noted)
A series of non-technical reports covering the volcano's behavior during the interval 20 March to 30 April are summarized in table 5. During this interval the hazard alert remained at yellow on a scale that encompasses the categories green (low), yellow, and red (high). The summaries documented a pattern of isolated explosions and occasional type-A seismic events.
|20 Mar 1997||After 12 hours of seismic quiescence, at 1020 on 20 March a 7-minute- long emission sent ash to 4 km altitude. Tephra fell NE and was reported as far as 18 km from the volcano.|
|31 Mar 1997||The level of activity remained low; only small A-type events were detected (up to M 3 on 30 March). During 26 to 31 March the average number of low-level emissions per day decreased from 12 to 2.|
|07 Apr 1997||A-type events were recorded sporadically; the largest occurred on 6 April (M 2.9 and 2.7). Emissions were infrequent and of moderate intensity.|
|11 Apr 1997||No more A-type events were recorded; activity was reduced to low-intensity exhalations.|
|16 Apr 1997||Slight increase in activity since 11 April, with a few small A-type earthquakes recorded. Low-intensity exhalations.|
|21 Apr 1997||Activity decreased starting on 19 April; however, the lava body inside the crater kept growing slowly.|
|25 Apr 1997||Microseismicity increased slightly on 23 April and at 1226 on 24 April a 15- minute explosive eruption sent an ash plume 4 km above the summit. Another smaller emission followed within 30 minutes. The wind carried the plume E. Activity decreased again on 25 April.|
|28 Apr 1997||Sporadic emissions of variable intensity. The largest on 26 April blew E and deposited ash.|
|29 Apr 1997||Major explosive eruption at 0110, followed by minor ones at 0122, 0159, and 0407. The first event caused ashfalls E of the volcano. Incandescent material was observed in the proximity of the volcano.|
|30 Apr 1997||Activity decreased; the last ejection occurred at 1131. Variable-intensity white-to-yellow fumarolic emissions.|
Three large explosions on 20 March and 24 and 29 April sent ash up to 4 km above the summit and caused tephra-falls on the NE slopes of the volcano.
The Satellite Analysis Branch of NOAA (SAB) conveyed several messages about the ash plume of April 24. The plume was seen in visible imagery moving E; one hour after the eruption started the plume was 65 km long and 8 km wide at an estimated height below 13 km. The plume remained visible in multi-spectral (MS) imagery for most of the following day, when a wedge-shaped ash cloud (maximum width at the leading edge reached 148 km) was moving NE at 100 km/hour at an altitude of ~6-8 km.
During the following weeks press agencies reported a major increase in activity. A sensationalistic Reuters news report described as "one of its most intense eruptions" of the past three years took place on the late evening of 11 May, with ash fall as far away as Veracruz city, 280 km E of the volcano.
On 27 May a message from a United Airlines flight noted ash moving ENE at ~13.3 km altitude, presumably related to another explosion. Visible satellite imagery the same day confirmed the presence of ash reaching the Gulf of Mexico and convective debris N and W of the summit.
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: Roberto Meli, Roberto Quaas Weppen, Servando De la Cruz-Reyna, Alejandro Mirano, Bertha López Najera, and Alicia Martinez Bringas, Centro Nacional de Prevencion de Desastres (CENAPRED); NOAA/NESDIS Satellite Analysis Branch (SAB), USA; Reuters.