Report on Pacaya (Guatemala) — 17 February-23 February 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
17 February-23 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, 17 February-23 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)
INSIVUMEH reported that seismicity at Pacaya increased around 0900 on 18 February. Incandescent material was ejected 200 m above Mackenney Crater and explosions produced gas-and-ash plumes that rose 450 m and drifted mostly NE and S. An active lava flow on the SSW flank was 1.1 km long and generated hot block avalanches from the flow front. A lava flow emerged on the SW flank on 19 February. During 19-20 February periods of increased activity lasted 3-5 hours; moderate-to-loud explosions were accompanied by rumbling and sounds resembling trains. Ballistics were ejected 300- 500 m from the crater and ash plumes rose as high as 450 m and drifted SW. Ashfall was reported in areas downwind including El Rodeo and El Patrocinio. A lava flow on the S flank was 800 m long and produced incandescent blocks from the flow front that descended 500 m.
Strombolian activity increased on the morning of 20 February but fluctuated throughout the day. Ash plumes, that were dense during periods of heightened activity, rose 450 m and drifted 10-25 km S, SW, and W. As it grew darker lava fountains were visible rising 300-400 m and ballistics were ejected as far as 500 m from the crater. The lava flow on the S flank had lengthened to 1.1 km. Strombolian explosions continued during 21-22 February, ejecting incandescent material 100-175 m high. Ash plumes rose 450-800 m above the summit and drifted possibly as far as 15 km NW, W, and SW, causing ashfall in areas downwind including San Francisco de Sales, El Cedro, El Rodeo, and El Patrocinio. Ballistics were ejected as far as 500 m from the crater. Blocks from the front of the lava flow descended 300 m. Weak explosions during 22-23 February ejected incandescent material as high as 100 m above the summit. A 900-m-long lava flow was active on the SSW flank. Ash plumes drifted 5 km S.
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.