This leads to increased erosion at the steepest parts, which is headward erosion. Geologically, the Schurwald is a dissected cuesta, formed by headward erosion. Pine Mountain is at the headward ramp of the Pine Mountain Thrust Fault. Headward erosion of the dam created a wide and long canyon. Possible explanations include headward erosion or a broken natural dam of a lake or river. However, headward erosion of the emergency spillway threatened to undermine and collapse the concrete weir.