Report on Rincon de la Vieja (Costa Rica) — February 1987
Scientific Event Alert Network Bulletin, vol. 12, no. 2 (February 1987)
Managing Editor: Lindsay McClelland.
Rincon de la Vieja (Costa Rica) Small explosion
Please cite this report as:
Global Volcanism Program, 1987. Report on Rincon de la Vieja (Costa Rica) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 12:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198702-345020.
Rincon de la Vieja
10.83°N, 85.324°W; summit elev. 1916 m
All times are local (unless otherwise noted)
"Alfonso Bustos of Upala, a town about 35 km NE of the volcano, reported that he observed an eruption of Rincón de la Vieja during the night of 31 December 1986. The seismological station of the Observatory, located on the volcano, registered an eruptive event at 2307:13 with a duration of 6 minutes 13 seconds. The period of highest amplitude was constant at one second.
"Because of weather problems in the region, we could not climb to the summit until 7 February 1987, when we verified that a small eruption had recently occurred. The affected area was the S and SE parts of the active crater, where eruptive materials were encountered to 500 m distance. At the crater rim, 10 cm of ash was measured and there were blocks 50 cm long by 40 cm wide. No evidence of juvenile material was encountered. Some plants had burns on their leaves, possibly caused by the acidity of ash deposited on them and the acidity of water that accompanied the ejecta; the eruptions occurred in a crater with a lake. The activity during the day of the ascent was constant emission of gas with a strong sulfurous odor that irritated the eyes and annoyed everyone that we encountered near the crater."
Geologic Background. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge that was 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. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of 1916-m-high Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A plinian eruption producing the 0.25 km3 Río Blanca tephra about 3500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.
Information Contacts: J. Barquero and E. Fernández Soto, OVSICORI.