Report on Turrialba (Costa Rica) — June 1998
Bulletin of the Global Volcanism Network, vol. 23, no. 6 (June 1998)
Managing Editor: Richard Wunderman.
Turrialba (Costa Rica) Fumarolic activity and small landslides continue; new fumaroles in April
Please cite this report as:
Global Volcanism Program, 1998. Report on Turrialba (Costa Rica) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 23:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199806-345070
Turrialba
Costa Rica
10.025°N, 83.767°W; summit elev. 3340 m
All times are local (unless otherwise noted)
During April-June, fumaroles on the NE, N, W, and SW flanks continued to discharge modest emissions with temperatures around 90°C (see plot, figure 3 in BGVN 23:03). Small landslides continued along the N and S walls of the principal crater.
Scientists collect condensate from one low-temperature fumarole one to three times per year. The temperature of this fumarole has remained stable at 89-90°C; however, the sulfate and chloride concentrations have varied from low values of around 5 ppm to values over ten-fold larger. The most recent reading was taken on 22 April 1997. The sulfate concentration, about 70 ppm, was higher than those for many of the past few years (see plot, figure 2 in BGVN 23:03 but note the correction below).
Around the time the higher sulfate concentration was measured, new fumaroles opened in the central crater, and the local seismic system registered increased monthly counts of high-frequency earthquakes (seen during both April and May, table 2). On 2 May a M 1.6 earthquake occurred at 7 km depth centered 6.5 km SW of the principal crater.
Table 2. Earthquakes at Turrialba during the first half of 1998. Courtesy of OVSICORI-UNA.
| Month | High-frequency | Low-frequency | Microseisms |
| Jan 1998 | 0 | 0 | 53 |
| Feb 1998 | 1 | 1 | 83 |
| Mar 1998 | 3 | 2 | 96 |
| Apr 1998 | 12 | 1 | 28 |
| May 1998 | 15 | 4 | 99 |
| Jun 1998 | 2 | 3 | 60 |
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. Fernandez, V. Barboza, E. Duarte, R. Saenz, E. Malavassi, M. Martinez, and Rodolfo Van der Laat, Observatorio Vulcanologico y Sismologico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica.
