Report on Pacaya (Guatemala) — 14 July-20 July 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 July-20 July 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Pacaya (Guatemala). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 14 July-20 July 2010. 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, after an increase in Pacaya's activity on 13 July, a decrease in seismicity was noted on 14 July. Strombolian explosions occurred on 14 July at 5-10 minute intervals, and occasional small pyroclastic flows traveled S. Gray ash plumes rose 500 m and drifted WSW. On 19 July, fumarolic plumes rose 100 m above MacKenney crater and drifted N. The seismic network had recorded a total of 120 explosions within the previous 24 hours. On 20 July Strombolian explosions generated ash plumes that rose 100 m and drifted 2 km N.
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.