Report on Pacaya (Guatemala) — 21 February-27 February 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 21 February-27 February 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Pacaya (Guatemala). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 21 February-27 February 2001. Smithsonian Institution and US Geological Survey.
14.382°N, 90.601°W; summit elev. 2569 m
All times are local (unless otherwise noted)
The agency responsible for monitoring active volcanoes in Guatemala, INSIVUMEH, observed several indications of renewed eruptive vigor at Pacaya. A local seismometer recorded over 700 earthquakes per day in comparison to 100 earthquakes per day recorded approximately 2 weeks earlier. SO2 gas emissions increased from 253 tons/day to 550 tons/day. In addition, lava was visible in the summit region at MacKenny Crater.
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.