In the 1930s, the glacier was found to be receding quickly. However, in 1963, a rock fall from Little Tahoma Peak covered the lower glacier with rock debris. The debris cover insulated the ice from melting. As a result of decreased melting, the glacier advanced rapidly in the early 1980s. That advance was continuing by 1992, but at a slower rate; ice beneath the rock debris was melting irregularly and forming a vast hummocky area. By 2003, the glacier was again retreating. In the past few decades the glaciers [in the American West] have been receding,