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Report on Irazu (Costa Rica) — April 1992


Bulletin of the Global Volcanism Network, vol. 17, no. 4 (April 1992)
Managing Editor: Lindsay McClelland.

Irazu (Costa Rica) Continued fumarolic activity; crater lake shrinks

Please cite this report as:

Global Volcanism Program, 1992. Report on Irazu (Costa Rica) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 17:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199204-345060


Costa Rica

9.979°N, 83.852°W; summit elev. 3432 m

All times are local (unless otherwise noted)

The main crater's fumarolic activity continued in April. Although temperatures remained similar at 88-91.5°C, the jet-engine sound heard in prior months was no longer audible. Between 12 February and 2 April, the crater lake's water level dropped 16 cm and the lake diameter shrank by 2 m. Cold and warm springs around the volcano showed no measurable changes in temperature or pH. The portable seismic net continued to record low-frequency earthquakes of low energy. Fewer than 10 events were recorded in April (at station "ICR", near the summit).

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: G. Soto and R. Barquero, ICE.