Report on Pacaya (Guatemala) — 24 February-2 March 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
24 February-2 March 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, 24 February-2 March 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 and CONRED reported that during 23-25 February explosions at Pacaya’s Mackenney Crater ejected incandescent material as high as 200 m. A lava flow, originating from a vent 300 m below the summit crater, was about 1.1 km long and produced incandescent blocks from the flow front that descended 300 m. more intense pulses of activity at the summit produced dense ash plumes that drifted more than 30 km S and SW. Ashfall was noted in areas downwind including Los Pocitos, Pacaya, El Rodeo, and El Patrocinio. Explosions continued during 26-29 February, although weather conditions sometime prevented visual confirmation.
RSAM data values notably increased during the morning of 1 March, reflecting an increase in Strombolian activity. Moderate-to-strong explosions ejected ballistics as high as 500 m above the summit. Ash plumes rose 1 km above the summit and drifted W and SW, causing ashfall at least in El Patrocinio. Incandescent material was ejected 150 m high, and ash plumes drifted W; ashfall was reported in El Patrocinio. The lava flow on the SSW flank was about 700 m long. On 2 March gas and ash plumes rose 150 m and drifted 2 km S. A lava flow on the SSW flank was 150 m long.
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.