Report on Pacaya (Guatemala) — 1 April-7 April 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 1 April-7 April 2009
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2009. Report on Pacaya (Guatemala). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 1 April-7 April 2009. 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 explosions in March ejected greater amounts of material that was deposited in the crater, enlarging the cones there. On 23 March, visual and audible changes in Strombolian activity were noted. Vigorous degassing produced sounds resembled airplane engines. In a report issued on 3 April, INSIVUMEH stated that Strombolian explosions from MacKenney cone during the previous few days ejected material 25 m into the air. On 2 April, lava flow volume increased, sending four lava flows W and one SW; the flows traveled 25-200 m. The seismic network detected tremor and explosions. On 6 April, lava flows on the W flank traveled 150-300 m, causing lava to pile up on the SW flank. Activity from MacKenney cone was continuous; one cone emitted gas and explosions about every 5-10 minutes, and a second cone ejected tephra 25 m high. On 7 April, one lava flow traveled 150 m W and one traveled 200 m SW. INSIVUMEH recommended that CONRED coordinate with authorities in Pacaya National Park to restrict visitors from climbing 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.