Report on Irazu (Costa Rica) — July 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 7 (July 1985)
Managing Editor: Lindsay McClelland.
Irazu (Costa Rica) Gas emission
Please cite this report as:
Global Volcanism Program, 1985. Report on Irazu (Costa Rica) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198507-345060
9.979°N, 83.852°W; summit elev. 3432 m
All times are local (unless otherwise noted)
Fumarolic activity continued on the N flank, with temperatures averaging about 60°C. A lake that started to form in the main crater in September 1984 was still present in July 1985. Bubbles from the gas emission could be seen rising through the lake water.
Geological Summary. 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: J. Barquero H. and E. Fernández S., Univ. Nacional, Heredia.