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This dissertation explores the combination of Interferometric Synthetic Aperture Radar (InSAR) results with field data to provide additional constraints on the processes controlling deformation signals observed at Galeras volcano (Colombia) and Santorini volcano (Greece). InSAR measurements during 2007-2008 at Galeras reveal a subsidence signal on its northeast flank. I model InSAR and gravity data to determine the best-fit parameters for the subsidence source and suggest this signal was caused by deflation of the magma chamber associated with the January 2008 eruption. In January 2011, Santorini volcano entered a period of unrest characterised by earthquake swarms and caldera-wide uplift. I analyse satellite data over a period incorporating both the preceding phase of quiescence (1993-2010) and the phase of unrest (2011-2012). A subsidence signal is confirmed on the intra-caldera island of Nea Kameni during 1993-2010. I investigate several possible scenarios for its source, with my preferred explanation being a combination of cooling and contraction of historic lava flows, and loading from these flows inducing relaxation of the substrate. I also use a joint InSAR/GPS inversion technique to model the caldera-wide uplift observed during 2011-2012. I determine the optimal parameters for the deformation source and the temporal variation in volume change within the shallow magma chamber. The renewed activity offered an opportunity to observe how soil-gas emissions would respond to an influx of magma to a shallow reservoir. I employ a new approach (222Rn-δ13C systematics) to identify and quantify the source of diffuse degassing at Santorini during the period of unrest. Finally, I present a new high-resolution merged LiDAR-Bathymetry grid, enabling detailed mapping of both onshore and offshore historic lava flows emplaced in the centre of Santorini caldera. Updated lava volumes provide new extrusion rate estimates and a means of estimating both the size and duration of future dome-building eruptions at Santorini. |
