Measuring and interpreting heat fluxes from shallow volcanic bodies using vertical temperature profiles: a preliminary test

To test the potential of heat flux prospecting in active volcanic areas usi ng shallow temperature data taken along vertical profiles, we carried out t wo thermal profile surveys, one not far from Yasur cone on Tanna Island, an d another inside the caldera of Ambrym (New Hebrides are, southwestern Paci fic). The basic steady heat flux of internal volcanic origin was determined , taking into account both conductive and convective heat transfers. At bot h locations there exists, over small distances, significant differences in the heat flux. These differences correspond to shallow sources of heat. The use of a network of vertical profiles allowed: (a) heat flux mapping; (b) location of shallow volcanic heat sources; and (c) observation of the detai led structure of the heat release at quiescent but active volcanoes.