Report on Pacaya (Guatemala) — October 1997
Bulletin of the Global Volcanism Network, vol. 22, no. 10 (October 1997)
Managing Editor: Richard Wunderman.
Pacaya (Guatemala) Eruptions continue in August and November
Please cite this report as:
Global Volcanism Program, 1997. Report on Pacaya (Guatemala) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 22:10. Smithsonian Institution.
14.382°N, 90.601°W; summit elev. 2569 m
All times are local (unless otherwise noted)
While visiting Guatemala City, Kent Johnson observed small explosions at Pacaya's summit on three hazy nights between 30 July and 4 August from vantage points ~40 km N of the volcano. The explosions sent lava clots into the air and lava flows down the side of the volcano; orange streaks of lava were observed traveling a short distance down the volcano's W slope. Through binoculars, the summit appeared orange with bright orange- yellow bursts occurring at ~5 minute intervals. During the day on 4 August, puffs of steam or ash were emitted from the summit. Hazy conditions made it difficult to photograph the emissions.
According to an 11 August aviation notice, Pacaya erupted around2100 on 9 August. Surface observations in Guatemala City indicated that the volcano was in eruption although no ash plumes were discerned in GOES-8 imagery during 11 August due to thunderstorms. Another aviation notice from Guatemala City reported an eruption at 0800 on 14 November. Although an ash cloud was reported by observers, the ash was not visible in GOES-8 visible or infrared imagery due to cloud cover.
Geological Summary. 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.
Information Contacts: Satellite Analysis Branch, NOAA/NESDIS, Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA; Kent Johnson, 7141 Jennifer Way, Sykesville, MD 21784 USA.