Report on Pacaya (Guatemala) — 3 February-9 February 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 February-9 February 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, 3 February-9 February 2021. Smithsonian Institution and US Geological Survey.
14.382°N, 90.601°W; summit elev. 2569 m
All times are local (unless otherwise noted)
On 6 February INSIVUMEH reported increased Strombolian activity and a higher number of explosions at Pacaya’s Mackenney Crater. The explosions rattled nearby houses and ejected ballistics as far as 500 m from the crater. Ash plumes rose as high as 650 m above the summit and drifted 5 km W, NW, and N. Ashfall was reported in areas downwind including San Francisco de Sales, El Cedro, Calderas, El Bejucal, and Mesías Altas. Lava effusion also increased and two active lava flows, 800 and 1,200 m long, were advancing. On 8 February ash plumes rose almost 600 m and drifted 30 km NW and W, and 10 km N. Explosions ejected ballistics as far as 300 m from the crater.
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.