TERRESTRIAL HEAT FLOW IN THE SWISS ALPS

Abstract

Terrestrial heat flow has been measured in three Alpine railroad tunnels. The geothermal gradients were calculated from temperatures measured during the construction of the tunnels, and corrections for topographic irregularities were made. The thermal conductivity of 113 rock specimens from the vicinity of the tunnels was measured. The heat flow in the Gotthard tunnel was found to be 1.6 × 10−6 cal/cm2 sec, in the Simplon 2.2 × 10−6 cal/cm2 sec, and in the Loetschberg 1.9 × 10−6 cal/cm2 sec. Most of the flux at the surface can be attributed to radioactive decay in a thickened crust, but a non-uniform distribution of radioactive elements may be required to explain the relatively high heat flow in the Simplon and Loetschberg tunnels.