Report on Pacaya (Guatemala) — 10 February-16 February 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 February-16 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, 10 February-16 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 a during 9-10 February Strombolian explosions at Pacaya’s Mackenney Crater ejected material 200-300 high and away from the crater. Ash clouds occasionally rose as high as 650 m and drifted 10 km W and SW. A 1.3-km-long lava flow was active on the S flank; block avalanches from the front of the lava flow descended 200 m. Activity increased around 1600 on 10 February. Strombolian explosions ejected incandescent material 500 m above the crater rim and produced gas-and-ash plumes that drifted W. Ashfall was reported in the villages of El Patrocinio (about 5 km W) and El Rodeo (4 km WSW). During 11-12 February material was ejected 300-500 m above the crater. Ash plumes rose 950 m and drifted N, causing ashfall in San Francisco de Sales (5 km N), San Jose Calderas, and Concepción el Cedro (9 km NNW).
Seismic data recorded pulses of increased activity during the morning of 12 February and again around 1400 on 13 February. Explosions ejected material 300-500 m above the crater. Ash-and-gas plumes rose almost 500 m and drifted 6 km W, N, and NE, causing ashfall in Santa Elena Barillas (6 km ENE), Mesillas Bajas (5 km NE), and Mesillas Altas. Another pulse of activity was recorded at 1145 on 14 February. Material was ejected as high as 250 m. Ash plumes rose less than 400 m and drifted 5 km E. A 650-m-long lava flow in the SSW flank was active on 15 February. Explosions continued to ejected material as high as 250 m above the vent.
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.