Proposal Abstract

Volcán Villarrica.

A four year-long project is presented with the main aim of studying the impacts of geothermal heating and eruptive activity on glaciers located on top of highly-active volcanoes in Southern Chile, in order to support decision making process regarding environmental and risk assessments in potentially affected areas. Until few years ago, it was believed that the strong thinning and shrink age of most of the glaciers of this part of the southern hemisphere was mainly a direct response to climatic changes observed in the meteorological network. However, glaciers capping active volcanoes may respond with differential behaviours depending on the intensity and type of volcanic activity, as well as to the geothermal influx of volcanic activity at their bases.Strombolian to plinian eruptions that occurred in the second half of the 20th century have partially affected and even completely destroyed glaciers existing within calderas or at the volcanic flanks. Few studies have been carried out to quantify these impacts in Chile, neither the regeneration of glaciers after eruptive events. In other cases, the existence of pyroclastic material on the surface of glaciers, has diminished surface ablation,preventing ice from rapid thinning, as observed on bare ice directly exposed to atmospheric warming. Thiseffect has been only partially studied at Volcán Villarrica where it was concluded that the thermal conductivityof the volcanic material played a crucial role, however, very little is known about the impacts of the wide variety of materials existing on nearby glaciers in southern Chile.

In the great majority of active volcanoes, the geothermal activity may have a direct incidence on basal ablation, however, up to date it has been difficult to measure the available melting energy at the glacier bed, or the effects of these geothermal fluxes on the hydrological balance of the glaciers. In several ice-capped volcanic complexes, ice-crevassing as a direct consequence of eruptive events has been recorded, however, this process has never been analyzed in detail,or properly documented and assessed in order to understand the influence on ice dynamics and or volumes.These non-climatic glacier responses could have dramatic consequences for the population living in the surroundings of volcanoes, therefore their characterization, quantification and modelling are crucial for a country like Chile, with such a large number of active volcanoes. Chilean glaciers on active volcanoes have received limited attention, partially due to logistic and weather constrains. The utilised techniques have been unable to obtain data from crevassed and steep areas, or during recurrent bad weather conditions affecting the glaciers. In order to improve and extend the survey efficiency, ground field campaigns must be complemented with remote sensing and airborne campaigns, capable of extending the coverage areas, intensifying data collection process and improving the accuracy of the results. This project proposes to study a selected group of the most active and partially documented ice-capped strato volcanoes of southern Chile, where we would like to carry out a detailed monitoring and measuring program, utilizing state of art techniques, including geodesy, helicopter/airborne laser altimetry, radio echo sounding, photographic cameras (ground/airborne), automatic weather stations including thermocouples for measuring underground temperatures, and ultrasonic gauges for hydrological measurements. These techniques will allow a better estimation of volume of water equivalent storage on each volcano, as well as measuring glacier changes in a wide spatial-temporal scale, from daily surface modifications on the ice surface, up to possible inter-annual volcanic edifice undulations/deformations.We hope to survey at sub-metric resolutions and accuracies three volcanoes distributed along the region (thecomplex of Nevados de Chillán, Villarrica and Hudson volcanoes), which together comprise an estimated ice area higher than 100 km2. We plan to study specifically the direct effects and consequences on surrounding areas of the following historical eruptions, different in magnitude as well as in duration: Villarrica, December of1971; Volcán Chillán/Volcán Nuevo, August of 1973; and Hudson, August of 1991. We will study in detail documentary records of these events, including maps/reports before the eruptions and compare them to afterward surveys, in order to determine glacier impacts and how glaciers recovered, but also to learn lessons upon the inherent risk of possible forth coming eruptions. The presence of volcanoclastic products generated during these eruptions and the geothermal field in the surroundings of the volcanoes will be also studied. The combination of these data will allow determining surface and basal glacier mass balances, yielding a better understanding of glacier dynamics and the effects of the volcanic activity. These new surveying techniques and methods, will improve the existing monitoring programs, intensifying and extending the discrete network of measurements actually available. The results of this project will contribute to a better understanding of glacier volcano interactions, separating them from possible climate change impacts on glaciers. The data generated by this project and its integration, through numerical modelling of possible lahar generation and inundation areas, will improve volcanic risk assessments, supporting decision processes, where government authorities,planners and urban designers need to intervene populated areas potentially under the influence of volcanic activity. The results of this project will also contribute to a better monitoring and understanding of glacier behaviour, from an area already affected by climate change, and from where water allocation rights competition is increasing, by among other factors, a number of projects expecting to use water resources partially generated by glacier melt, for hydro-electrical power generation plants. In this sense, this project is a direct contribution to decision-making processes in the context of a highly-needed national strategy plan for Chilean glaciers.