Large-scale Topographic Changes at Erupting Volcanoes Measured by the TanDEM-X Digital Change Map

Volcanic eruptions cause large-scale topographic changes, through the emplacement of lava flows and lava domes, the formation of craters and calderas, and thick ash and pyroclastic deposits. Here we analyse the TanDEM-X Digital Change Map (DCM), which compares the DEM produced during 2010-2015 with satellite acquisitions collected in 2016-2022. The DCM covers 142 eruptions at 89 volcanoes; the data was good quality at 34 of these but not useable at 25. Topographic changes associated with volcanic activity was visible at 49 volcanoes including lava flows, domes, intrusions, pyroclastic flows, lahars, tephra fall, crater formation and landslides. We analyse five case studies in detail: Sierra Negra, Galápagos; Erta Ale, Ethiopia; Sangay, Ecuador; Ebeko, Russia and Nabro, Eritrea. Our measurements of the lava flows at Sierra Negra and Nabro and crater formation at Ebeko agree to within 15% of previous measurements, confirming the accuracy of the TanDEM-X DCM in volcanic areas. At Erta Ale, we find maximum lava thickness of >40 m, greatly exceeding previous field-based estimates (<2.5 m); consequently, our total volume estimate is an order of magnitude higher. At Sangay, the patterns of height change are consistent with local reports, but our measurements have high uncertainties due to the prevalence of vegetative noise and steep topography. Overall, we demonstrate that the TanDEM-X DCM can measure topographic changes at volcanoes, and in many cases allows us to make new measurements. Finally, we discuss the lessons learned from the TanDEM-X DCM for planning future satellite missions, including the upcoming ESA Harmony Mission.