A decade of high-resolution remote sensing observations of topographic changes and ground deformation at Semeru volcano

At Semeru volcano, dome growth, lava emplacement, and pyroclastic density currents commonly occur over short timescales within sustained eruptive activity, producing rapid and large-amplitude changes in topography and surface deformation. In this type of andesitic system, quantifying these processes remains challenging due to their small temporal and spatial scales and their location in steep summit areas where ground-based measurements are rare. Here, we show that the combined analysis of multi-temporal topography and high-resolution ground deformation provides quantitative constraints on these processes at the scale of the volcanic edifice. Between 2015 and July 2021, the edifice experienced progressive accumulation of material, with a net volume bounded between 24.008 ± ± 0.114 and 24.219 ± ± 0.114 Mm ^3 3 . This construction phase was followed by a major reorganization following the December 2021 eruption, associated with dome collapse and the emplacement of large pyroclastic density currents, resulting in a net volume loss bounded between −30.946 ± ± 0.034 and −30.995 ± ± 0.034 Mm ^3 3 . X-band Interferometric Synthetic Aperture Radar (InSAR) time series reveal localized deformation affecting recent pyroclastic deposits on the southeastern flank, with displacement rates of 2 to 4 cm.yr ^-1 - 1 consistent with long-term gravitational adjustment, while no clear evidence of sustained post-eruptive magmatic inflation or deflation is detected. These results demonstrate that jointly analyzing topographic changes and ground deformation improves the interpretation of satellite observations in rapidly evolving volcanic environments.