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Report on Pacaya (Guatemala) — 18 September-24 September 2019


Pacaya

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 18 September-24 September 2019
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2019. Report on Pacaya (Guatemala) (Sennert, S, ed.). Weekly Volcanic Activity Report, 18 September-24 September 2019. Smithsonian Institution and US Geological Survey.

Weekly Report (18 September-24 September 2019)

Pacaya

Guatemala

14.382°N, 90.601°W; summit elev. 2569 m

All times are local (unless otherwise noted)


A special report from INSIVUMEH noted that seismic activity at Pacaya continued to increase, with RSAM values reaching 8,000 units by 18 September, coincident with an intensification of explosive activity at Mackenney Crater. Explosions from a growing cone in the crater ejected material as high as 100 m above the cone. Lava effusion increased; several lava flows (300-500 m long) advanced on the N and NW flank towards Cerro Chino and produced avalanches of blocks up to 1 m in diameter from the flow fronts. Strombolian explosions during 19-24 September ejected material 5-25 m above the cone, though on 21 September material was ejected as high has 100 m. Two lava flows traveled SW on 21 September.

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.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)