Activity of Popocatepetl and Colima Volcanoes,
México

Servando de la Cruz-Reina, Institute of Geophysics, UNAM/CENAPRED
Roberto Quaas Weppen, CENAPRED
Based on a communiqué by the Scientific Advisory Team on Colima Volcano and the State Civil Protection Systems of Colima and Jalisco, 10 September 1999

The Popocatepetl volcano began showing renewed signs of activity in 1993, both seismic and eruptive, until 21 December 1994, when it produced its first ashfall in 70 years, alarming the population and the authorities. Some of the more vulnerable towns on the northeastern side had to be evacuated.

On 5 March 1996, the volcano entered a new phase of activity, with ash eruptions comparable to those of December 1994. At the end of March 1996, a growth in a dome of lava at the bottom of the crater was detected. Several significant explosions accompanied this growth. The largest one took place on 30 April 1996, when five mountain-climbers, ignoring the warnings, were killed when they were climbing the volcano. The dome kept growing moderately until July 1996, when it began to shrink.

The event of 30 June 1997 was the most severe since the renewal of activity in late 1994. The eruption was preceded by a series of volcano-tectonic quakes, with magnitudes going from 2.0 to 2.7, which were detected over a 13-minute period. This eruption generated an enormous plume that soon stretched 8 km over the volcano. The intensity of the eruption was estimated at between 2 and 3 on the VEI scale, and the Scientific Committee recommended that the volcanic alert be set for several hours to red, the highest warning level, although no evacuation was carried out.

The analysis of the different parameters that CENAPRED monitors is aimed at explaining to the authorities and the public the degree of volcanic activity and its evolution in clear language that can allow anyone to understand the situation. An itinerant exhibition was put together, including a scale model of the volcano and its surrounding, to further the understanding of the phenomenon by the population.

Since the 30 June event, a yellow volcanic alert remains in place. However, on the recommendation of the Scientific Committee, Civil Protection authorities also remain in a high state of preparedness.

The Colima volcano experienced mudslides and lahars during 5 and 6 May 1999 due to heavy rains, especially on the southern and southwestern slopes of the volcano, in the La Lumbre and El Cordobán streams.

The possibility remains that an event similar or greater than the one that took place on 10 February 1999 may occur, so immediate response mechanisms remain in place for the population at risk, under the coordination of the State Civil Protection Systems and the Mexican Army.

The activity exclusion zone remains in place in both States, some 6.5 km from the top of the volcano. The immediate response mechanism for evacuating settlements up to 8.5 km away from the summit remains in place, as does the preventive warning radius of 11.5 km from the summit.

For more information, please contact:
CENAPRED
Tel. (525) 424-6100 Fax (525) 606-1608
mailto:difusiónensayes-l@cenapred.unam.mx