The beheading of the Inn Valley at Maloja Pass, which took place between 29,400 - 14,500 years before present, is one of the major geologic events in the Quaternary of this sector of the Alps. Three valleys that formerly presumably fed the Inn Glacier but were redirected into the Bregaglia Valley by a large collapse that caused the beheading. Tectonic stresses exercised by movements along the Engadine Line may have caused the collapse which left a steep escarpment at Maloja Pass and a large elevation difference between the Inn and Bregaglia valleys.