Capturing Nyiragongo’s Dynamics: Synergistic InSAR and Thermal Infrared Observations for Volcanic Hazard Assessment across the 2021 Nyiragongo Eruption

Nyiragongo volcano, located in the western branch of the East African Rift (DR Congo), is among the world's most active and hazardous volcanoes. Its proximity to the densely populated city of Goma and to Lake Kivu, a CO2- and CH4-rich hydrogeological reservoir, makes pre- and rapid syn-eruptive hazard assessment critical, as demonstrated by the devastating impact of the January 2002 eruption on people and infrastructure.On May 22, 2021, a new eruption produced extensive lava flows and significant co-eruptive surface deformations, prompting urgent assessment of the underlying magmatic and tectonic dynamics. We considered multi-orbit Sentinel-1 InSAR data to map the two-dimensional co-eruptive deformation field. Night-time Landsat thermal infrared imagery was used to quantify pre- and post-eruptive heat flux and assess its association with eruptive dynamics and deformation patterns. Interferograms reveal spatially heterogeneous deformation, indicating multiple deformation sources that reflect the combined influence of shallow magmatic intrusions, regional tectonic adjustments, and surface fracture propagation. Field observations by the Goma Volcano Observatory corroborate the satellite-detected displacements, confirming the location, orientation, and evolution of major fractures in eastern Goma.The ultimate objective of this research is to establish an integrated, multi-sensor volcanic monitoring framework. By quantitatively linking InSAR-derived deformation with thermal infrared observations, we are able to capture the dynamic interplay between magmatic processes and surface responses. This synergistic approach provides a robust tool for hazard assessment and risk mitigation in densely populated regions of the East African Rift, bridging observational data with actionable decision-support for emergency management. Finally, this synergistic approach, combined with recent and upcoming advances in sensor capabilities, would open new avenues for space-based early-warning systems.