Report on Pacaya (Guatemala) — 17 March-23 March 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
17 March-23 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, 17 March-23 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 reported periods of intense activity at Pacaya’s Mackenney Crater during 17-18 March. Explosions produced dense ash plumes that rose 500-1,000 m above the crater rim and drifted 25-30 km S, SW, W, NW, and N. Incandescent material was ejected 300-500 m above the crater and fell within a 600 m radius of the crater. Lava flows on the S flank were 1.5 km long and set fire to vegetation at the advancing edge. Two new lava flows were visible; one traveled 400 m E and the other traveled 500 m S. Ashfall was reported in El Rodeo (4 km WSW), Patrocinio (about 5 km W), El Cedro (9 km NNW), San Francisco de Sales (5 km N), Amatitlán (12 km N), and Villa Nueva (16 km N).
Strong explosions during 21-23 March generated dense ash plumes that rose as high as 1.5 km above the summit. The plumes drifted 25-30 km NE, E, SE, and S, causing ashfall in Los Llanos, Los Pocitos (5 km S), Los Dolores (6 km SE), El Rodeo, Patrocinio, Mesías Alta and Mesías Baja, and Santa Elena Barillas (6 km ENE). Incandescent material was ejected 500 m above the crater and fell within 300-600 m of the crater. A lava flow on the SW flank was 1.5 km long, a flow on the S flank was 300 m long, and the E-flank lava flow had lengthened to 500 m. On 23 March ash plumes drifted 50 km NW, N, and NE, causing ashfall in Pepinal San Francisco de Sales, Los Pocitos, Los Dolores, Mesías Altas and Mesías Bajas, Santa Elena Barillas, Villa Nueva, and in the capital of Guatemala City (25-30 km NNE). Ash fell at Guatemala's international airport, Aeropuerto Internacional La Aurora, 50 km N of Pacaya, causing the airport to close. Soldiers swept ash off of the runway and incoming flights were diverted to El Salvador.
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.