Overdeepenings : valleys buried beneath the surface

Valleys are key components of our landscape, with rivers and glaciers the main drivers behind their formation through erosion. When formed by a river, valleys are referred to as fluvial valleys, identifiable by their V-shaped geometry, given by a narrower valley floor, while glaciers yield glacial valley by eroding in a U-shape, where the valley bottom is flat and wider. Here we focus on glacial valleys, in particular the deep basins found beneath them called overdeepenings, to investigate the exact processes behind their formation. These structures occur in currently and formerly glaciated landscapes, such as this studyís site located in Switzerland, and are challenging to investigated as they are often buried beneath sediments or hosting lakes. By using gravity data and 3D numerical modelling, we obtained the geometry of overdeepening, unveiling possible formation mechanisms involving a combination of water-based erosion and glacial abrasion.