INSIVUMEH and CONRED reported that during 2-6 March strong Strombolian explosions at Pacaya’s Mackenney Crater produced ash plumes that rose as high as 1 km above the summit and drifted W, SW, and S. Tephra fell in areas downwind including El Patrocinio (5 km W), El Rodeo (4 km WSW), San Francisco de Sales (5 km N), El Cedro (9 km NNW), Calderas (3 km N), and Las Jazmines (5 km W), and in the municipalities of Palín (10 km WNW) and Escuintla (22 km SW). Periods of lava fountaining were visible, and incandescent material was ejected 300-1,000 m high. Three lava flows were active and all had several branches; one traveled SSW, one traveled S, and one on the SE flank was 800-1,200 m long. During 6-8 March strong explosions ejected material as high as 500 m and produced dense ash plumes that rose up to 1 km. Lava flows continued to be active, sometimes producing block avalanches from the ends. On 8 March the S-flank flow was about 850 m long and continued to generated block avalanches. Strong explosions during 8-9 March ejected ballistics 300-500 m away from the crater. Dense ash plumes rose up to 1.5 km and drifted 30 km SW and S. The lava flow on the S flank was 900 m long and shed blocks from the end.

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.

Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH), Coordinadora Nacional para la Reducción de Desastres (CONRED)