Report on Irazu (Costa Rica) — February 1993
Bulletin of the Global Volcanism Network, vol. 18, no. 2 (February 1993)
Managing Editor: Edward Venzke.
Irazu (Costa Rica) Decreased fumarolic activity continues
Please cite this report as:
Global Volcanism Program, 1993. Report on Irazu (Costa Rica). In: Venzke, E. (ed.), Bulletin of the Global Volcanism Network, 18:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199302-345060.
9.979°N, 83.852°W; summit elev. 3432 m
All times are local (unless otherwise noted)
Fumarolic activity in the main crater continued at a decreased level. The surface of the yellow-green crater lake rose about 12 cm from 1 December to January, but then dropped 40 cm by 15 February. Lake temperature ranged from 17.4 to 24.5°C. Areas along the edge of the lake with bubbles and gas emissions decreased in number and intensity, and had temperatures less than 92°C. The pH of the water has continued to rise since the low measurement of 5.7 on 15 February. The "steaming ground" on the debris fan N of the lake had fewer active fumaroles, and a maximum temperature of 87.9°C. There were no changes in the temperature or pH of the hot springs around the 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: G. Soto and R. Barquero, ICE.