Report on Rincon de la Vieja (Costa Rica) — September 1994
Bulletin of the Global Volcanism Network, vol. 19, no. 9 (September 1994)
Managing Editor: Edward Venzke.
Rincon de la Vieja (Costa Rica) Vigorous fumarolic activity
Please cite this report as:
Global Volcanism Program, 1994. Report on Rincon de la Vieja (Costa Rica) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 19:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199409-345020
Rincon de la Vieja
Costa Rica
10.8314°N, 85.3364°W; summit elev. 1729 m
All times are local (unless otherwise noted)
Fumarolic activity in the main crater remained vigorous during August and September. Preliminary processing of seismicity recorded by ICE with a portable digital station 2.2 km S of the crater during fieldwork in late August indicated several hundred low-frequency earthquakes beneath the crater, and background tremor-like activity. The preliminary interpretation is that the low-frequency seismicity is caused by hydrothermal circulation among a shallow magma body, aquifers, and the lake system. The OVSICORI-UNA seimic station (5 km SW of the active crater) registered 15 high-frequency low-magnitude events during September.
From the village of México (40 km NE), early morning observations during late September and early October by an ICE geologist revealed a steam-rich gas column rising up to 1 km above the crater. This is higher than the 300-400 m estimated in March.
Geological Summary. Rincón de la Vieja is a volcanic complex in the Guanacaste Range of NW Costa Rica. Sometimes referred to as the Rincon de la Vieja-Santa María Volcanic Complex, it consists of a slightly arcuate 20-km-long ridge of 12 craters and pyroclastic cones constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. The Santa María cone, the highest peak of the complex, is located on the E side of the ridge and has a lake within the 400-m-diameter crater. A Plinian eruption producing the 0.25 km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous reported eruptions possibly dating back to the 16th century, have been from the active crater, near the center of the complex, with an acidic 300-m-diameter lake.
Information Contacts: E. Fernandez, J. Barquero, V. Barboza, R. Van der Laat, T. Marino, F. de Obaldia, and L. Carvajal, OVSICORI; G. Soto, W. Taylor, F. Arias, G. Alvarado, and R. Barquero, ICE; Mauricio Mora, Univ. de Costa Rica.
