Report on Irazu (Costa Rica) — December 1981
Scientific Event Alert Network Bulletin, vol. 6, no. 12 (December 1981)
Managing Editor: Lindsay McClelland.
Irazu (Costa Rica) No activity observed
Please cite this report as:
Global Volcanism Program, 1981. Report on Irazu (Costa Rica) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 6:12. Smithsonian Institution.
9.979°N, 83.852°W; summit elev. 3432 m
All times are local (unless otherwise noted)
"The summit was visited on 19 November and 5 December. No activity was observed [but see 7:5 and 7:11]."
Geologic Background. Irazú, one of Costa Rica's most active volcanoes, rises immediately E of the capital city of San José. The massive volcano covers an area of 500 km2 and is vegetated to within a few hundred meters of its broad flat-topped summit crater complex. At least 10 satellitic cones are located on its S flank. No lava flows have been identified since the eruption of the massive Cervantes lava flows from S-flank vents about 14,000 years ago, and all known Holocene eruptions have been explosive. The focus of eruptions at the summit crater complex has migrated to the W towards the historically active crater, which contains a small lake of variable size and color. Although eruptions may have occurred around the time of the Spanish conquest, the first well-documented historical eruption occurred in 1723, and frequent explosive eruptions have occurred since. Ashfall from the last major eruption during 1963-65 caused significant disruption to San José and surrounding areas.
Information Contacts: R. Stoiber, S. Williams, H.R. Naslund, J.B. Gemmell, D. Sussman, Dartmouth College; D. Fajardo, Instituto de Investígaciones Sismicas, Nicaragua; E. Malavassi R. and J. Barquero H., Univ. Nacional, Heredia.