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. Plain Language Summary: We used data from two satellite systems, Sentinel‐1 and Cosmo‐SkyMed, to study Ol Doinyo Lengai, the only active carbonatitic volcano on Earth located in Tanzania. We analyzed hundreds of radar satellite images over a decade to understand changes in the ground deformation. By separating data from different orbits of the satellites and comparing them, we found that the ground at the volcano's summit was sinking at a rate of approximately 3.6 cm per year. Through simple geodetic modeling, we concluded that this sinking was likely caused by a shallow deflating magma reservoir, less than one km deep below the summit. This conclusion aligns with other scientific studies focusing on the volcano's petrology and geophysics. Key Points: InSAR time series show a ∼0.5 km diameter subsiding area around the summit crater at Ol Doinyo LengaiThe subsidence is likely due to a deflating shallow magma reservoir (point‐source)The modeled reservoir is less than 1 km deep below the summit crater, consistent with geophysical and geochemical studies [ABSTRACT FROM AUTHOR]