Beginning 30 May, Strombolian eruptions ejected ash clouds from MacKenney Crater [see also BGVN 12:07]. Explosions occurred twice/minute and were accompanied by rumbling. Lava flows were observed on the N flank.

After about 3 hours of increasingly vigorous harmonic tremor, a strong eruption occurred on 14 June at 1930. At El Caracol, 3 km SW of the crater, 10 cm of ash fell in 3 hours, collapsing the roofs of two houses. About 600 residents were evacuated. Lava flowed SW and was continuing to advance two days later. As of 16 June, an ash column rose 2-3 km above the crater and tremor of 15 mm amplitude was continuing.

Geological Summary. Eruptions from Pacaya 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 older Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1,500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate scarp inside which the modern Pacaya volcano (Mackenney cone) grew. The NW-flank Cerro Chino crater 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 covered the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit.

Information Contacts: E. Sánchez, Edgar Quevec, and Enrique Molina, INSIVUMEH; Norman Banks, USGS.