Alpbachtal

The Alpbachtal is what geologists call an exposed anticline. These are layers that are folded into the shape of an A (see figure). The core (or bottom layer) of that anticlinal structure consists of slate. However, the largest part of the top of that 'A' in the Alpbach Valley has been eroded away (=exposed). This is related to the fact that slate weathers much faster than, for example, the slightly younger limestone layer. The slate is also water-retaining, so the water penetrates it little and mostly flows off it. As a result, it erodes faster than the limestone, which you find mainly on the northern peaks (Gratlspitze and Hochstrickl).

The slate dates back to the Ordovician. The limestone dates from the Devonian.

Pascal Brackman