Report on Pacaya (Guatemala) — 20 January-26 January 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 January-26 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, 20 January-26 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)
Strombolian activity and lava effusion continued at Pacaya during 19-26 January. Explosions from the cone in Mackenney Crater ejected material as high as 200 m above the vent. Occasionally ash plumes rose no higher than 200 m above the summit and drifted as far as 10 km W, SW, and S. Moderate-to-strong Strombolian explosions on 22 January generated ash plumes that drifted NW and caused ashfall in the regions of San Francisco de Sales and San Vicente Pacaya. The explosions rattled nearby structures. Lava flows were active on the S and SW flanks; avalanches from the S flow front reached the base on the volcano and the SW lava flow traveled as far as 1.7 km by 25 January.
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.