GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.2 GNGTS 2024 in two difuse degassing zones (Fig. 2, T gradient). The new HTF sites are located within two radial fractures elongated in the outer fank of the northern slope, with the outlet temperature reaching 320 °C, at the tme of installaton (December 2023). In the zones of difuse degassing we have choosen two monitoring sites in a ground secton of pyroclastc breccia (Fig. 2, T gradient), where we buried four sensors, at diferent depths. These difuse degassing zones (DDZ) generally show at the surface a mild thermal anomaly because the ground is heated by the massive condensaton of steam at shallow depth (a few meters below the line of sensors). At the tme of installaton of the monitoring profle (VSCS in …, G-Termis in November 2023, Fig. 2) the ground was permeable and dry, with temperature increasing at depth. In the DDZ, in the absence of water and steam, heat transfer is essentally difusive and the convectve component is negligible. In this dry conditon, the temperature gradient is a proxy of the surface heat fux, being the only variable directly related to it. Moreover, the extrapolaton of temperature gradient to the boiling temperature suggests a reference level for the minimum depth where the rising steam condenses within the ground. So, the contnuous monitoring of the temperature gradient allows to track the local changes in heat fux and the vertcal movements of the steam front in the summit area, at distance from the HTF zone. The G-Termis staton is located about 190 m (linear distance) to the east of HTF zone, whereas the VSCS staton is located about 210 m to the west of HTF zone (Fig. 2). Fig. 1 – The longest tme series of fumarole temperature recorded at La Fossa crater. The map showing the geochemical network is on the lef corner.