Report on Pacaya (Guatemala) — March 1990
Bulletin of the Global Volcanism Network, vol. 15, no. 3 (March 1990)
Managing Editor: Lindsay McClelland.
Pacaya (Guatemala) Continued weak Strombolian explosions; low SO2 flux
Please cite this report as:
Global Volcanism Program, 1990. Report on Pacaya (Guatemala). In: McClelland, L (ed.), Bulletin of the Global Volcanism Network, 15:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199003-342110.
14.382°N, 90.601°W; summit elev. 2569 m
All times are local (unless otherwise noted)
Volcanologists from INSIVUMEH and Michigan Tech visited Pacaya on 13, 14, 17, 18, and 28 February and 1, 2, 3, and 4 March, and flew over the volcano on 16 February. The following is from their report.
"Activity at Pacaya continued at a low level, consisting of brief (10-60 second), weak (ejecta typically thrown 2-100 m), Strombolian explosions with reposes of <1 to several minutes. All activity was from a small cone, 6 m high and 8 m wide at its rim, within MacKenney crater. The explosions were accompanied by gas emission (with jet-like noise) and often by fine ash clouds.
"On 17 February, during activity that was typical of the observation period, 78 COSPEC scans were made from a ground observation site 1.25 km from MacKenney crater (at Cerro Chino). Pacaya was emitting SO2 at an average rate of 30 t/d, with the measured range varying between 3 and 130 t/d. Higher fluxes were directly associated with observed small explosions. The new SO2 observations at Pacaya were much lower than values measured several times from 1972 until 1980 (Stoiber et al., 1983; reference under Santiaguito), which were generally between 250 and 1,500 t/d."
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: Otoniel Matias and Rodolfo Morales, Sección de Volcanología, INSIVUMEH; W.I. Rose, Jimmy Diehl, Robert Andres, Michael Conway, and Gordon Keating, Michigan Technological Univ.