Report on Irazu (Costa Rica) — September 1988
Scientific Event Alert Network Bulletin, vol. 13, no. 9 (September 1988)
Managing Editor: Lindsay McClelland.
Irazu (Costa Rica) Fumarolic activity continues; rain forms two crater lakes
Please cite this report as:
Global Volcanism Program, 1988. Report on Irazu (Costa Rica). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 13:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198809-345060.
9.979°N, 83.852°W; summit elev. 3432 m
All times are local (unless otherwise noted)
For the past several years, fumarolic activity on the NW flank has continued unchanged. Because of intense precipitation during August and September, small greenish lakes have recently formed in the main crater and Diego de la Haya crater. No signs of solfataric degassing have been observed in the lakes.
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: G. Soto, Escuela Centroamericana de Geologia & Red Sismologica Nacional, Univ de Costa Rica.