Report on Pacaya (Guatemala) — 8 September-14 September 2020
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 September-14 September 2020
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2020. Report on Pacaya (Guatemala). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 8 September-14 September 2020. Smithsonian Institution and US Geological Survey.
14.382°N, 90.601°W; summit elev. 2569 m
All times are local (unless otherwise noted)
On 13 September INSIVUMEH reported that during the previous week activity at Pacaya’s Mackenney Crater was characterized by lava-flow effusion and Strombolian explosions that ejected material as high as 200 m above the vent. Ejected material landed within 50 m of the cone. An active lava flow that had traveled NE was 1,250 m long; another on the N flank was as long as 300 m. Explosive activity rattled houses within a 4-km radius. Lava flows continued to be active during 13-15 September; reaching 600 m long on the NE flank, 300 m long on the N flank, and 400-425 m long (and most active) on the S flank. Strombolian explosions continued to ejected material as high as 200 m.
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.