Erupciones < 3800 a.P. del Volcán Rincón de la Vieja, Costa Rica

Abstract

Rincón de la Vieja is the only active volcano in the Guanacaste Range. Its activity has been characterized by frequent gas and steam emissions, and periodical phreatic and phreatomagmatic eruptions (isolated or clustered in 5-7 year intervals, every 40 ± 10 years), normally accompanied by hot lahars, concentrated mainly on its Caribbean watershed. Prehistoric pyroclastic flows (1520 B.P.) have been mapped and described, as far as 10 km from the active crater. A sub-plinian layer (3770 B.P.) is preserved on the WSW flank, in accordance with the prevailing trade winds. Both deposits have pumice and scoria. The pumices are geochemically and petrographically similar, but scoriae are different. Scoriae from the pyroclastic flows are more similar to those erupted recently. This suggests that remnant dacitic magma from the subplinian eruption, was erupted due to the intrusion of andesitic magma, which once erupted, formed scoria-pyroclastic flows. This latter magma has remained in a shallow reservoir and would have fed the eruptions of the last 1500 years.