Linking long-term magma evolution and short-term volcano deformation

Volcanoes often change shape over timescales of months to decades, and such signals are likely influenced by the long-term physical evolution of magmatic systems over hundreds of thousands to millions of years. The link between these different timescales is often overlooked. In this presentation, I will show how volcanic surface deformation in response to a sudden overpressure at depth evolves over the long-term history of magmatic systems. To do this, I integrate thermal models of large-scale magma system evolution with thermo-mechanical simulations of surface deformation. We examined how changes in magma flux, magmatism duration over hundreds of thousands of years, and the depth of an overpressure source impact post-injection viscoelastic surface movement over a 10-year period. Our findings show that the duration of the long-term magmatic activity and magma supply rate significantly affect surface deformation over timescales of years. The results show that due to thermal heterogeneity in the crust, asymmetrical patterns of surface deformation can emerge in time due to viscoelastic processes, potentially similar to temporal patterns of magma movement. When uplift originates from deep sources (around 10 or 15 km below the surface), deformation follows a consistent uplift trend, dissipating within a few years with little dependence on past magma flux or system lifespan. Conversely, shallow sources (around 5 km below) display a strong dependence on long-term magma supply rate and system lifespan, resulting in distinct patterns of post-intrusive subsidence and subsequent uplift for colder magma systems, or exclusive uplift for hotter and longer-lived systems. These findings align exceptionally well with the deformation behaviour and geophysical tomography at Tullu Moye and Aluto volcanoes in the East Africa Rift. In conclusion, understanding how long-term magmatic processes interact with short-term volcano deformation is crucial for interpreting signals of volcanic unrest.