Thermal Monitoring of Volcanoes from Space

Volcanic eruptions transfer a significant amount of heat from the earth's crust to the atmosphere. Thermal monitoring of volcanoes from space aims to detect and measure this heat in real-time (or near real-time) and track its variations in space and time before, during, and after an eruption. In this chapter, I introduce the physical principles of thermal remote sensing applied to volcanology as well as the main systems and the online tools currently used for operational thermal monitoring of volcanoes. These systems are based on platforms and sensors with different spatial, temporal, and spectral characteristics, each of which is well situated to detect volcanic phenomena with specific spatial and temporal scales (from the slow appearance of small fumaroles to the very rapid emission of large lava flows). In particular, I present the range of metrics currently used to quantify a thermal anomaly from space and I highlight how the integration of multiple datasets provides a deeper insight into the volcanic activity in progress. Finally, by using real cases I provide a series of best practices in analysing and interpreting thermal signals during unrest phases or eruptive crises. This chapter summarizes the great progress made by this discipline in the last 20 years and highlights the fundamental contribution that thermal remote sensing can make in monitoring various types of volcanic activity.