Expected temperature zones at the top of the Lochkovian petrothermal reservoir. Full circles indicate towns of at least several thousand inhabitants. Hatched and cross-hatched areas mark possible and inferred deep hydrothermal reservoirs (HR), respectively. Contour of Eifel plume according to Keyser et al. (2002). In the white hatched zone temperatures are particularly uncertain due to missing thermal data or an unreliable geology.