The Shoulders of Glacial Troughs

Abstract

The inner or immediate trough of a glaciated valley is now generally regarded as very closely related in origin to the glacier that last flowed in it, being equally a result of its erosive work whether vertically excavated or laterally opened by it. This is the Trog of Richter (1900), which he regarded as more or less exactly containing the glacier of the last glaciation during at least a great part of the period of trough-development, though signs of overflow at the height of the ice flood are found above the “shoulders” which bound the trough. Rarely does the trough comprise the whole valley: more commonly shoulders distinctly separate steep trough walls from gentler upper valley-side slopes. In addition to the inner trough-side shoulders, however, higher benches are in many cases unmistakably present, though they may be poorly defined and are always discontinuous, so that their correlation and restoration as a definite number of actual upper shoulders is by no means certain.