Report on Pacaya (Guatemala) — 2 July-8 July 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 2 July-8 July 2003
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2003. Report on Pacaya (Guatemala). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 2 July-8 July 2003. Smithsonian Institution and US Geological Survey.
14.382°N, 90.601°W; summit elev. 2569 m
All times are local (unless otherwise noted)
On 5 July at 0715 a very thin ash and/or gas plume was visible at Pacaya on satellite imagery at a height of ~3 km a.s.l. extending ~7.5 km SW. By 1430 the plume was no longer visible, possibly obscured by thunderstorm clouds in the area, and the Guatemala Volcano Observatory reported that only steam was emitted from Pacaya.
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.