The fault lies at the bottom of a valley at Gemmi Pass (close to Leukerbad, Valais) between elevation. It cuts through carbonates, sandstones and shales of the Helvetic nappes; the rocks are of Jurassic-Eocene age and were folded during the Oligocene-Miocene. Hot springs at Leukerbad and a Tertiary dyke at the Trubelstock close to the fault indicate elevated geothermal gradients in the ground. The fault was discovered with the help of aerial photography followed by field studies and trenching.