Report on Pacaya (Guatemala) — February 1994
Bulletin of the Global Volcanism Network, vol. 19, no. 2 (February 1994)
Managing Editor: Richard Wunderman.
Pacaya (Guatemala) Strombolian activity continues
Please cite this report as:
Global Volcanism Program, 1994. Report on Pacaya (Guatemala). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 19:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199402-342110.
14.382°N, 90.601°W; summit elev. 2569 m
All times are local (unless otherwise noted)
Pacaya continued to erupt on a regular basis. Between late afternoon on 5 February and sunrise on 6 February, Stephen O'Meara photographed and videotaped various stages of moderate eruptive activity from a vantage point about 4 km SSW of the summit (about half-way between the villages of Los Pocitos and El Caracol). Strombolian activity had increased markedly since he visited the volcano in November 1993. Strombolian fountains rose 100-200 m, and some of the larger ash clouds rose upwards of 400 m. An incandescent lava flow emerged from a single opening in MacKenney crater and traveled down the SW flanks. That main flow then divided into two separate lobes, each of which had several rivulets. Incandescent boulders continually rolled down the flank from the fronts of these flows. The longest flow extended to about 1,800-m elevation.
Activity was strong in the late afternoon, weak in the morning, and throughout the night eruptions occurred about once every minute. In the afternoon, the ash plumes appeared dark gray or black and sometimes there were 3-4 ash ejections in rapid succession. Stronger ejections were usually inaudible, but when visible activity waned in the early evening, noises like "rolling thunder" and "a lions roar" prevailed. At other times the observers noted noises like "the ebb and flow of waves pounding a cliff." More powerful blasts in this interval produced detectible earth movements.
Geologic Background. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.
Information Contacts: Stephen O'Meara, Sky & Telescope.