Mineral layers that do not reach the surface here are the Lower Bunter, running from a depth of some 90 m underneath the town (about 110 m above sea level) down to some 390 m farther down, and, following at yet greater depths, Upper and Lower Zechstein from the Permian. From this layer come the two mineral springs in Bad Hersfeld. This layer is also used in underground mining from the 400-metre level on down on the Werra (Heringen, Philippsthal) and on the Fulda (Neuhof bei Fulda), yielding potash.