Reconstructing palaeo-volcanic geometries using a Geodynamic Regression Model (GRM): Application to Deception Island volcano (South Shetland Islands, Antarctica)

This article describes a reconstruction made of the palaeo-volcanic edifice on Deception Island (South Shetland Islands, Antarctica) prior to the formation of its present caldera. Deception Island is an active Quaternary volcano located in the Bransfield Strait, between the South Shetland Islands and the Antarctic Peninsula. The morphology of the island has been influenced mainly by the volcanic activity but geodynamics and volcanic deformation have also contributed. A volcanic reconstruction method, the Geodynamic Regression Model (GRM), which includes a terrain deformation factor, is proposed. In the case of Deception Island, the directions of this deformation are NW–SE and NE–SW, and match both the observed deformation of the Bransfield Strait and the volcanic deformation monitored over the last 20 years in the island, using Global Navigation Satellite System (GNSS) techniques. Based on these data, possible volcanic deformation values of 5–15 mm/yr in these directions have been derived. A possible coastline derived from a current bathymetry is transformed, according to values for the chosen date, to obtain the palaeo-coastline of Deception Island of 100 k years ago. Topographic, geomorphologic, volcanological and geological data in a GIS system have been considered, for computation of the outside caldera slope, palaeo-coastline, palaeo-summit height and palaeo digital elevation model (DEM). The result is a 3D palaeo-geomorphological surface model of a volcano, reaching 640 m in height, with an increase of 4 km3 in volume compared to the current edifice, covering 4 km2 more surface area and the method reveals the previous existence of parasite volcanoes. Two photorealistic images of the island are obtained by superposition of textures extracted from a current Quick Bird satellite image also. This technique for reconstructing the terrain of an existing volcano could be useful for analysing the past and future geomorphology of this island and similar locations.

► Reconstruction of an island previous to the formation of its caldera is proposed.
► Input data: topography, bathymetry, pre-caldera deposits and deformation rates.
► Taken into account: mass balance due to ice, erosion and sea level.
► The palaeo-summit height calculated for the palaeo-stratovolcano is 640 m.
► The method reveals the pre-existence of parasite volcanoes.