Significant increase in relief of the European Alps during mid-Pleistocene glaciations

Some of Earth's greatest relief occurs where glacial processes act on mountain topography(1,2). This dramatic landscape is thought to be an imprint of Pleistocene glaciations(3,4). However, whether the net effect of glacial erosion on mountains is to increase(5-7) or decrease(8-10) relief remains disputed. It has been suggested that in the European Alps, the onset of widespread glaciation since the mid-Pleistocene climate transition(11) led to the growth of large, long-lived and strongly erosive alpine glaciers(12,13) that profoundly influenced topography(14). Here we use He-4/He-3 thermochronometry(15) and thermal-kinematic models to show that the Rhone Valley in Switzerland deepened by about 1-1.5 km over the past one million years. Our results indicate that while the valley was incised and back-cut, high-altitude areas were preserved from erosion. We find an approximately two-fold increase in both local topographic relief and valley concavity, which occurred around the time of the mid-Pleistocene transition. Our results support the proposed link(12-14) between the onset of efficient glacial erosion in the European Alps and the transition to longer, colder glacial periods at the middle of the Pleistocene epoch.