On Steam-Driven Thermal Anomalies at Active Volcanoes Through Laboratory and Numerical Experiments

At active magmatic-hydrothermal systems, volatile circulation and surface thermal anomalies are known to be related. However, the specific interconnections between permeable gas flow, H₂O condensation, and heat transport remain poorly understood. This study investigates the potential of steam released from boiling aquifers to generate surface thermal anomalies. Novel laboratory experiments were conducted by injecting hot steam into a permeable material to examine how material characteristics and flow dynamics affect heat propagation. The experimental results are analyzed using numerical models based on heat conduction (CM) and a combination of heat conduction and advection (CAM) to provide a reference for extending laboratory knowledge to natural volcanic systems. Laboratory results include: (a) steam-driven thermal anomalies are more sensitive to changes in flow rates than variations in steam temperature; (b) condensation depth significantly affects the surface thermal response, with shallower condensation resulting in earlier detection; and (c) a low initial water content in the medium drastically reduces the detection time, while further increase in water content have minimal effect. The CAM model fits experimental results better than the CM, suggesting that non-condensed vapor flows through the surface at active volcanoes. A thermal anomaly of 1 K is estimated to appear at the surface approximately 0.7–120 years after degassing begins in the underlying hydrothermal system. The emergence of these anomalies depends on crust permeability, thermal properties, steam flow dynamics, and hydrothermal system depth. Quantifying these parameters is crucial, as they influence the detection of thermal anomalies, a key precursor to volcanic eruptions.