Report on Pacaya (Guatemala) — November 1978
Scientific Event Alert Network Bulletin, vol. 3, no. 11 (November 1978)
Managing Editor: David Squires.
Pacaya (Guatemala) Strong, continuous steam emission unabated since February
Please cite this report as:
Global Volcanism Program, 1978. Report on Pacaya (Guatemala) (Squires, D., ed.). Scientific Event Alert Network Bulletin, 3:11. Smithsonian Institution.
14.382°N, 90.601°W; summit elev. 2569 m
All times are local (unless otherwise noted)
The strong continuous steam emission that began in late 1977 from MacKenney Crater was still underway when Pacaya was visited on 16 November 1978, unabated in intensity since February.
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: W. Rose, Jr., Michigan Tech. Univ.