Report on Pacaya (Guatemala) — December 1986
Scientific Event Alert Network Bulletin, vol. 11, no. 12 (December 1986)
Managing Editor: Lindsay McClelland.
Pacaya (Guatemala) Ejected blocks cause at least 12 injuries, damage roofs
Please cite this report as:
Global Volcanism Program, 1986. Report on Pacaya (Guatemala) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 11:12. Smithsonian Institution.
14.382°N, 90.601°W; summit elev. 2569 m
All times are local (unless otherwise noted)
On 21 January at 1520 lapilli and blocks were ejected onto the N flank [see also 12:1]. In the town of Calderas (roughly 3 km N of the vent), 12 people were injured, the zinc roofs of 25 houses were perforated, and coffee crops were damaged by 1/4-kg blocks about 25 cm in diameter. Residents of Calderas quoted by UPI said that blocks obstructed roads to flank villages. Blocks also caused several grass fires and killed some animals. In Santa Elena Barillas (roughly 6 km NE of the vent), Mesillas Bajas (roughly 5 km NE), and Mesillas Altas (roughly 4 km NNE), 3 cm of ash fell. Newspapers reported that rescue workers were trying to evacuate about 100 residents from a sparsely populated area near the volcano. As of the morning of 22 January the volcano was quiet.
Geological Summary. 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: E. Sánchez and Edgar Quevec, INSIVUMEH; UPI; AP.