Satellite Geodesy Unveils a Decade of Summit Subsidence at Ol Doinyo Lengai Volcano, Tanzania

The processing of hundreds of Synthetic Aperture Radar (SAR) images acquired by two satellite systems: Sentinel-1 and COSMO-SkyMed reveals a decade of ground deformation for a ∼0.5 km diameter area around the summit crater of the only active carbonatitic volcano on Earth: Ol Doinyo Lengai in Tanzania. Further decomposing ascending and descending orbits when the appropriate SAR data sets overlap allow us to interpret the imaged deformation as ground subsidence with a significant rate of ∼3.6 cm/yr for the pixels located just north of the summit crater. Using geodetic modeling and inverting the highest spatial resolution COSMO-SkyMed data set, we show that the mechanism explaining this subsidence is most likely a deflating very shallow (≤1 km depth below the summit crater at the 95% confidence level) magma reservoir, consistent with geochemical-petrological and seismo-acoustic studies.