The frequent lahar threats to communities around Rincón de la Vieja Volcano, Costa Rica

Abstract

The Rincón de la Vieja (10º 49′ 40″ N, 85º 19′ 42″ W, 1700 m a.s.l.), andesitic stratovolcano is located at about 25 km NE of Liberia city, in NW Costa Rica, on the Guanacaste volcanic range. Its historical volcanic activity takes place in the Active Crater (hosting a 200 m wide hot-acidic lake), is characterized by the occurrence of several phreatic and phreatomagmatic eruptive events that produce frequent lahars affecting mainly the northern low lands. Minor effects by ash, water contamination and acid rain are brought by these episodes to other communities in other directions. Rincón has had several eruptions in the last 40 years, being the most recent; 1966-67, 1983, 1987, 1991, 1995 and 1998. Communities like Dos Ríos de Upala, Gavilán, Buenos Aires and others are subject to frequent threats besides their common hazards by their hostile weather. Located some 7 km North from the active crater these communities have endure in the past the loss of plantations, bridges, roads and communication among them. No specific local emergency plans have been designed to these communities. An informal alert system was set up by the National Emergency Commission and fortunately since it was installed there has not been the chance to test its usefulness. Meanwhile communities are in need of organization and understanding of the elements threatening them. Only in recent years some of these communities around volcanoes have been taken into account in regional emergency governmental plans. Very few have specific organizational, response, evacuation or preparedness plans. Thus, they have been historically neglected to play a primary role in volcanic emergency plans. Specific studies to assess perception, level of organization, resources and capabilities will be needed in the near future in order to create fundamental links between scientists, state emergency agencies and settlers.