Here at the beginning of the gorge near Schwarzenbruck there is an information board about the natural monument.
The Schwarzach Gorge is an approximately 2.2 km long and gorge-like river valley south of Schwarzenbruck in the Middle Franconian district of Nürnberger Land in Bavaria. It is named after the Schwarzach river.
The entire gorge has been a designated 41-hectare nature reserve since 1936.
The small river Schwarzach has cut deep into the Burgsandstein between the Schwarzenbruck district of Gsteinach and the bridge canal of the Ludwig-Danube-Main Canal. The middle castle sandstone was formed about 215 million years ago during the Mesozoic (Triassic). This type of rock is widespread in western and southern Middle Franconia[6].
Hard and resistant rock like the Burgsandstein narrows a valley to a gorge. The erosive power of the river could only cut into the rock along fissures and faults. The hard sandstone types form the steep gorge walls. Less hard rock layers such as clay layers and weak zones led to the riparian areas being undermined, especially during high water. This resulted in scours, overhanging roofs and surf caves. The two largest caves of this type are the Karl's Cave and the Gustav Adolf Cave.
The river owes its increased erosive power to a geological event about 1.5 million years ago. At that time, the Main broke through the Steigerwald near Eltmann and from then on it no longer flowed south towards the Danube, but west into the Rhine. All Main-Franconian rivers, including the Schwarzach, had a shorter route to the sea and steeper gradients as a result of this diversion. In the Altdorf and Burgthann area in particular, this led to the formation of imposing Räth Gorges such as the Teufelskirche in Grünsberg.