A Synergistic Thermal Framework to Classify, Quantify, and Monitor Volcanoes from Space

Volcanic heat flux offers a direct window into subsurface magmatic processes and eruption dynamics, yet its quantification from space remains incomplete. Current satellite-based assessments are largely restricted to high-temperature eruptive activity, resulting in the systematic omission of moderate- and low-temperature sources. We integrate Mid-InfraRed (MIR; 3.5-4.5 μm) and Thermal-InfraRed (TIR; 10-12 μm) satellite observations into a unified analytical framework capable of resolving the full range of volcanic thermal emissions.

We introduce the Total Volcanic Radiative Power (VRP_Tot), defined as the combined contribution of MIR- and TIR-derived radiative power (VRP_MIR + VRP_TIR). This approach yields temperature-robust radiative power estimates (within ±20%) over 273-1500 K interval, whereas single-band methods exhibit systematic errors exceeding 90% when applied beyond their operational temperature thresholds. To further characterise thermal behaviour, we define VRP_Ratio, a dimensionless indicator of volcanic thermal structure that effectively distinguishes hydrothermal, dome-forming, open-vent, and effusive regimes within a common parameter space.

Application of this framework to representative volcanoes demonstrates that inventories relying solely on MIR observations underestimate total thermal output by factors of 2-20 for moderate-temperature systems, indicating that global volcanic heat fluxes may be substantially higher than previously recognised. At Sabancaya volcano, temporal variations in VRP_Ratio reveal changes in thermal structure several months prior to the November 2016 eruption, signals that are undetectable using single-wavelength approaches.

This transferable methodology enables more accurate assessments of global volcanic heat budgets and enhances the early identification of eruptive transitions, representing a significant advance in satellite-based volcano monitoring. Furthermore, these results resolve long-standing biases in volcanic heat-flux inventories, enhance real-time monitoring capabilities, and have broad implications for volcanology, climatology, and planetary science.