Upper Rhine Plain

The Upper Rhine Plain, Rhine Rift Valley or Upper Rhine Graben is a major rift, about 350km and on average 50km, between Basel in the south and the cities of Frankfurt/Wiesbaden in the north. Its southern section straddles the border between France and Germany. It forms part of the European Cenozoic Rift System, which extends across central Europe. The Upper Rhine Graben formed during the Oligocene as a response to the evolution of the Alps to the south and remains active to the present day. Today, the Rhine Rift Valley forms a downfaulted trough through which the river Rhine flows.FormationThe Upper Rhine Plain was formed during the Early Cenozoic era, during the Late Eocene epoch. At this time, the Alpine Orogeny, the major mountain building event that was to produce the Alps, was in its early stages. The Alps were formed because the continents of Europe and Africa collided. It is thought that because the collision was irregular, the initial contact between the two continents resulted in the formation of dilational (extensional) structures in the foreland basin to the north of the Alps. The result was substantial crustal thinning, forming a major extensional graben and causing isolated volcanic activity. The stretch factor is estimated to be ~2.