Upper Rhine Graben

The Upper Rhine Graben, also called the Upper Rhine Plain or Rhine Rift Valley, is a major rift about 350 kilometers long and 50 kilometers wide on average, running between Basel in the south and Frankfurt and Wiesbaden in the north, its southern stretch straddling the border between France and Germany. It formed in the Late Eocene as part of the early Cenozoic response to the collision of Europe and Africa during the building of the Alps, which put the crust north of the mountains under extension; geologists estimate the resulting stretch factor at roughly two, thinning the crust and opening the dilational structure that today carries the Rhine River along its floor. It belongs to the wider European Cenozoic Rift System that runs across central Europe and remains geologically active, having also triggered isolated volcanic activity in the surrounding region. This entity documents the Upper Rhine Graben specifically as a geological formation, the rift structure itself, distinct from the Rhine River that flows through it.