Report on Pacaya (Guatemala) — January 1990
Bulletin of the Global Volcanism Network, vol. 15, no. 1 (January 1990)
Managing Editor: Lindsay McClelland.
Pacaya (Guatemala) Gas bursts and minor Strombolian spattering but no lava flows
Please cite this report as:
Global Volcanism Program, 1990. Report on Pacaya (Guatemala) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 15:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199001-342110
14.382°N, 90.601°W; summit elev. 2569 m
All times are local (unless otherwise noted)
Gas bursts from MacKenney Crater's inner crater vent were observed during fieldwork between 1500 and 1730 on 4 January. The gas bursts, of varying intensity and duration, occurred about every 15 minutes. Some were accompanied by Strombolian spattering; the most energetic lasted several seconds and ejected spatter to 40 m height. A mound of agglutinated spatter was centered around the 1-m-wide vent. The inner crater was about 60 m in diameter and 30 m deep, with its S wall against the inner wall of MacKenney Crater. Rockfalls were frequent on the steep inner crater walls. Near the inner crater rim, the floor of MacKenney Crater was muddy and strewn with small blocks of spatter. Residents of the area said that this part of the crater floor had recently been occupied by a small lake. Active fumaroles were abundant along the upper E wall of MacKenney Crater. No active lava flows were evident.
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: S. Halsor, Wilkes Univ; C. Chesner, Eastern Illinois Univ.