Report on Irazu (Costa Rica) — December 1982
Scientific Event Alert Network Bulletin, vol. 7, no. 12 (December 1982)
Managing Editor: Lindsay McClelland.
Irazu (Costa Rica) Fumarolic activity on the NW flank
Please cite this report as:
Global Volcanism Program, 1982. Report on Irazu (Costa Rica) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 7:12. Smithsonian Institution.
9.979°N, 83.852°W; summit elev. 3432 m
All times are local (unless otherwise noted)
Fumarolic activity was limited to the NW flank of the volcano. Temperatures oscillated between 78°C and 85°C. No activity was observed in either the principal crater or Diego de la Haya, just to the SE.
Activity on a local fault caused an earthquake swarm 4 June. The swarm generated landslides in the wall that divides the principal crater from Diego de la Haya. Another stronger swarm occurred 23-24 September affecting the area between Irazú and Turrialba volcano.
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, R. Naslund, C. Connor, J. Prosser, and J. Gemmell, Dartmouth College; E. Fernández S. and J. Barquero H., Univ. Nacional, Heredia.