INSIVUMEH reported that during 9-10 January explosions at Pacaya ejected lapilli up to 70 m above the crater. White and blue fumarolic plumes drifted SE, and the seismographs recorded constant tremor. On 11 January Strombolian activity was observed, and new craters on the E, S, and W flanks produced lava flows as long as 1.5 km. Activity from the main crater increased; explosions ejected tephra 75 m high and gas plumes rose 200-600 m. CONRED reported evacuations from Villa Canales (14 km NW), El Chupadero (2-2.5 km S), and San Vicente Pacaya (5 km NW). INSIVUMEH noted that RSAM values decreased throughout the day. Activity further decreased on 12 January. Explosions ejected tephra 100 m above the crater and gas plumes rose 200-300 m. Lava effusion, Strombolian activity, and seismicity declined. During 12-13 January lava effusion remained low and lava flows reached 2.8-3 km long. Bluish-white gas plumes rose 300 m. During 13-14 January Strombolian activity ejected lapilli as high as 70 m, and blue and white plumes drifted S.

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)