Skip to content

A hydromechanical deformation model for Deception Island caldera, South Shetland Islands

Jasmine Dibben 1, James Hickey 1 and Adelina Geyer-Traver 2

  • Affiliations:  1 Department of Earth and Environmental Sciences, University of Exeter, Penryn, UK; 2 Geociencias Barcelona (GEO3BCN), Barcelona, Spain

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 44

  • Programme No: 2.3.30

  • Theme 2 > Session 3

Abstract

Deception Island (DI) is 13 km wide active caldera in the South Shetland Islands, popular for polar research and Antarctic tourism. Ground deformation monitoring in the austral summer since 1999 shows 3-to-6-year inflation-deflation cycles, hypothesised as resulting from hydrothermal activity. Evidence supporting an active DI hydrothermal system includes heated soils and waters, fumaroles, bubbling gases, and gaps in an otherwise island wide permafrost. Deformation modelling at DI is currently limited, and thus far has not examined the role of hydrothermal unrest. We use numerical modelling to investigate how fluid injection in hydromechanical models, using DI topography and inferred subsurface structure, influences simulated unrest. Our models test varying subsurface structures, ranging from a homogeneous basalt to a heterogeneous crust with vertical and horizontal contacts. Different fluid injection locations and the influence of a high porosity ring fault are also investigated. We show that altering the model's subsurface geology and structural properties, including the fault, strongly influences the ground surface deformation: heterogenous models show reduced ground surface displacement compared to a homogeneous model; adding the fault focuses deformation within the caldera; while adding fractured basalt to the caldera base flattens the maximum deformation region across the model interior bay. Our results also indicate that fluid injection location strongly controls the spatial deformation pattern. Despite this, using a more geologically heterogeneous model configuration reduces the deformation differences caused by different fluid inlet types, indicating that fluid injection placement and use of heterogeneous subsurface geology should be considered when building hydromechanical models.