Report on Irazu (Costa Rica) — December 1993
Bulletin of the Global Volcanism Network, vol. 18, no. 12 (December 1993)
Managing Editor: Edward Venzke.
Irazu (Costa Rica) Crater lake rises 20 cm
Please cite this report as:
Global Volcanism Program, 1993. Report on Irazu (Costa Rica). In: Venzke, E. (ed.), Bulletin of the Global Volcanism Network, 18:12. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199312-345060.
9.979°N, 83.852°W; summit elev. 3432 m
All times are local (unless otherwise noted)
During November, greenish-turquoise water in the crater lake at Irazú rose 20 cm and supported subaqueous fumaroles in the N and SE. Summaries of the behavior of the crater lake, including chemical data that suggests similarities to other quiescent volcanic systems, appeared in earlier reports (18:1 and 5).
Irazú inflated at a rapid rate in 1991, but it has only deformed a limited amount since then (18:1 and 3). For November the network of dry-tilt meters measured insignificant change. Seismicity was unreported in October and November, but when reported in 1993 it was generally at low levels.
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: E. Fernández, J. Barquero, R. Van der Laat, F. de Obaldia, T. Marino, V. Barboza, and R. Sáenz, OVSICORI.