Smithsonian Institution
Global Volcanism Network Bulletin v. 20, no. 4, April 1995

Rincon de la Vieja (Costa Rica)  Description of the crater lake and

Rincon de la Vieja
Costa Rica
10.83N, 85.33W; summit elev. 1,916 m

The remote Rincon de la Vieja volcanic complex continues to display
unsettled seismic and fumarolic activity. OVSICORI-UNA reported
that during April fumarolic venting continued from the W wall,
creating noise audible from the crater's rim. Escaping gases stung
the skin. Radial fractures encircled the crater on its NE, N, and
NW sides.
G. Soto (ICE), Jean-Philippe Ran on, and Gorges Boudon climbed the
volcano on 1 May and reported that the lake contained a scum of
floating sulfur and was pale turquoise in color. No lake
temperature measurements were made but the entire surface steamed
slightly. In contrast to a previous visit in March 1994, the lake
level seemed significantly higher, although the amount has yet to
be quantified from photographic records; zones of bubbling
(previously several meters across) were absent.
Fumaroles on the crater's inner SE wall were quite active and fumed
noiselessly. Gas plumes, clearly visible from the volcano's N
flank, rose up to 100 m above the crater before being blown by the
wind. Small, steam-rich fumaroles adjacent to concentric fractures
surrounded the crater, typically near the 1,640 m contour. These
fumaroles were also active last year.
At least two other noteworthy fumaroles, expelling steam and
sulfurous gases, sit on the N flank (along the valley called
Quebrada Azufrada at around 1,200- and 1,300-m elevation). In clear
weather, these fumaroles are visible from local villages and
residents stated that they had been active for the past several
Information Contacts: Erick Fernandez, Vilma Barboza, and Jorge
Barquero, Observatorio Vulcanologico y Sismologico de Costa Rica,
Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia,
Costa Rica; Gerardo J. Soto, Oficina de Sismologia y Vulcanologia
del Arenal y Miravalles: OSIVAM; Instituto Costarricense de
Electricidad (ICE), Apartado 10032-1000, San Jose, Costa Rica;
Jean-Philippe Ran on, BRGM, Orleans, France (presently at USGS
Cascades Volcano Observatory, 5400 MacArthur Blvd., Vancouver, WA
98661-7095 USA); Gorges Boudon, Observatoires Volcanologiques,
Institut de Physique du Globe de Paris, 4 Place Jussieu, 75252
Paris 05, France.