Metamorphosis of Gneiss

Gneisses are formed under high temperature/pressure conditions within the earth, and getting to the surface through erosion and/or plate tectonic events such as the Alpine folding. During the metamorphosis no new materials are formed, but the raw materials (mainly feldspar, mica and quartz) are recomposed. This example makes apparent, what forces impinged on the rock, in order to deform it so strongly. The Alpine folding and the erosion by the Massa river made the today’s gneiss visible.