Practical evaluation of steady heat discharge from dormant active volcanoes: case study of Vulcarolo fissure (Mount Etna, Italy)

From a theoretical approach combined with experimental study, I propose a method to compute both sensible and latent heat transfer in a thermally active volcanic area. This method is applied to a fumarolic thermal fissure located on the south flank on Mount Etna (Italy). The method involves four steps: (1) mapping of Self-Potential (SP) to quickly identify thermal anomalies; (2) mapping of ground temperature (T) at constant depth in the area defined by SP mapping; (3) measurement of vertical T profiles at selected representative stations including the coldest and hottest; and (4) direct measurements of vapor flow where the convective heat flux reaches the surface. When heat flux values vary in the range 10–300 W m−2, T measurements at a depth equal to about 1 m are sufficient to estimate the absolute flux value to within an absolute error less than 30%, and 10% for the relative value. Ground temperature measurement is an easy and accurate method for estimating heat discharge on a limited surface to define the fissure system, monitor time variations of heat flux, or to calibrate remote sensing results on the ground.