Long-Term Magma Dynamics and Volcanic Deformation, with Application to the Western Galápagos

Ground deformation at volcanic centres is complex, and primarily occurs as a response to volume changes in the underlying magmatic system, providing insight into the dynamics of magma migration and storage. Syn-eruptive displacements are well studied due to their high-magnitude, and inform us about the depth and geometry of the source that fed the eruption, the location of any eruptive fissures, as well as the location and geometry of any conduits between the source and the surface, such as a dike. However, volcanic ground displacements during periods of eruptive quiescence are arguably more informative, given their use in eruption forecasting (e.g. an uptick in uplift prior to an eruption), and in evaluating changes in magma supply. Here, I use satellite Interferometric Synthetic Aperture Radar to investigate long- term displacements at established magmatic reservoirs, with particular focus on vol- canoes of the Western Galápagos. I synthesise observations of displacement from the complete geodetic record, and make new observations from 2015–2022, using Sentinel-1 data. I consider these observations in context of the eruptive and petrological record for each volcano to propose a new, unrest-based classification for Western Galápagos volcanism. I then analyse the Sentinel-1 time series in detail, and show that volca- noes here routinely undergo correlated deformation with one another. I propose that there is a regional, bottom-up, magmatic control on this behaviour. Finally, I consider long-term observations of volcanic subsidence, using examples from the Galápagos and around the world, to investigate the role of crystallisation on magmatic volume loss and deformation. Through these three studies, I showcase the complex interactions between magmatic processes, and volcanic surface deformation. By making novel observations of volcanic ground displacement at multiple volcanoes, I provide new insight into the workings of volcanic systems, and demonstrate the utility of InSAR when considered alongside other petrological and geophysical techniques.