Report on Pacaya (Guatemala) — 6 January-12 January 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 January-12 January 2021
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2021. Report on Pacaya (Guatemala). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 6 January-12 January 2021. Smithsonian Institution and US Geological Survey.
14.382°N, 90.601°W; summit elev. 2569 m
All times are local (unless otherwise noted)
INSIVUMEH reported that the lava flow that began on 2 January from a vent on the SW flank, 200 m below Pacaya’s Mackenney Crater, formed 3-4 branches and was 400 m long by 6 January. Avalanches of material descended the W, SW, and S flanks. Strombolian explosions produced ash plumes that rose 100-150 m above the cone and drifted 10 km S and SW. Explosions on 7 January produced ash plumes that rose 300-500 m above the crater and ejected ballistics 300 m away from the crater. Explosions rattled structures in nearby villages. Two new lava flows emerged on the N flank at 0740; one traveled 50 m and the other 200 m. Active lava flows on the W and SW flanks were 550 m long. Overnight during 7-8 January a new lava flow on the SW flank descended 425 m. During 9-12 January Strombolian explosions continued to ejected material up to 300 m above the cone. The lava flow on the SW flank reached a length of 1.2 km on 9 January and 1.5 km by 10 January; it remained active through 12 January. Ash plumes drifted 10 km W during 10-11 January, and avalanches form the crater area descended the SW and S flanks.
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.