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Report on Turrialba (Costa Rica) — August 1996


Bulletin of the Global Volcanism Network, vol. 21, no. 8 (August 1996)
Managing Editor: Richard Wunderman.

Turrialba (Costa Rica) Fumaroles at 90°C with pH values of ~4

Please cite this report as:

Global Volcanism Program, 1996. Report on Turrialba (Costa Rica) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 21:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199608-345070


Costa Rica

10.025°N, 83.767°W; summit elev. 3340 m

All times are local (unless otherwise noted)

During July observers witnessed weak fumarolic activity continuing along the NE, N, W, and S sides of the crater. Small landslides were prevalent along the main crater's N, S, and W walls. Annual fumarole temperature and condensate pH measurements (figure 1) show a rough correspondence with variations in other observed activity. Seismicity recorded at station VTU (0.5 km E of the active crater) during July included 146 local earthquakes. In August, local earthquakes took place 299 times; some of their signals had dominant frequencies around 2.5-4.0 Hz.

Figure (see Caption) Figure 1. Turrialba's annual fumarole temperatures and condensate pH values, 1992-1996. Courtesy of OVSICORI-UNA.

Geological Summary. Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive edifice covers an area of 500 km2. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.

Information Contacts: E. Fernández, E. Duarte, V. Barboza, R. Van der Laat, E. Hernandez, M. Martinez, and R. Sáenz, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica.