Recent changes in total ice volume on Volcán Villarrica, Southern Chile

Abstract

Results obtained by the first intensive airborne surveys carried out at Volca´n Villarrica (39 S) in Southern Chile, are presented. These campaigns included the use of a scanner laser system, for detecting the glacier surface topography, and a helicopter-borne ice penetrating radar, for measuring ice thicknesses. These surveys allowed determining the snow and ice volume storage at this volcano, volume which is susceptible to melt during eruptive events generating dangerous fast flows (lahars). Volca´n Villarrica is one of the most active volcanoes in Chile, with frequent eruptive events, many of them associated with lahars which are considered the most hazardous process at this volcano. In fact, most of the casualties and infrastructure damages incurred during historical eruptive events at the volcano are associated with lahars. With use of the radar and laser data, a total volume of 1.17 ± 0.1 km3 of water equivalent (w.eq.) at the volcano in 2012 was calculated, only 37 % of the estimated volume of 1961, a reduction mainly explained by the area shrinkage and ice thinning rates observed in the last 51 years. This total volume represents a lower boundary available for melting during eruptive events when lahars mudflows can be generated, because mainly in the winter, nearly 0.14 km3 w.eq. are potentially added to the volcano as temporal snow falls. The volume of water equivalent lost in recent decades does not mean a lower risk associated with these flows, as there has been a huge increase in populated areas in the surroundings of the volcano in recent years.