Results of geoelectrical surveys in the area of Crater 70, Deception Island, Maritime Antarctica

Abstract

Deception Island is horse-shoe shaped stratovolcano with 15 km diameter and a large caldera that opens towards the southeast, forming a bay about 7 km wide. The maximum altitude is at Mount Pond (539 m a.s.l.). About 57% of the island area is covered by glaciers. In geological terms Deception Island is composed of volcano-sedimentary deposits, including pyroclastic flows and deposits, strombolian scoriae and lava, volcanic and hypo-volcanic indurated ashes, and phreatomagmatic deposits. Recent eruptions took place in the interior of the island in 1967, 1969, and 1970. Permafrost is widespread in the island but its characteristics are still poorly studied. In this study we present geoelectrical data collected in the Crater 70 area of Deception Island which was formed during the eruptions of 1970. The study area is located in the southern slope of a volcanic cone and the objective of the geoelectrical survey was to determine if there were any permafrost aggradation after the eruptive event and to assess the thickness of the frozen body. Two electrical resistivity tomography (ERT) profiles and a vertical electrical sounding (VES) were done (Fig. 1). Geoelectrical methods are particularly well adapted to study the spatial distribution of permafrost because of its high electrical resistivities in comparison with the electrical resistivities of soil and rocks with water and above 0 oC.