| Cirques are formed by the headward erosion of a mountain glacier. Under the
weight of accumulated snow and ice at the head of a river valley, a mountain glacier
plucks away at the head of the valley over several hundreds of years sculpting the valley
head into a natural amphitheater.
Figure 7.3 Pawnee cirque from the air The view form the air gives us a better perspective of the distribution of landforms
found in Pawnee cirque. The rock glaciers are easily identified from their tongue-like
shape. Talus, fragments of rock, collect at the bottom of the headwall after
having fallen off is face.
The terrain of Pawnee Cirque is illustrated in the topographic map. The cirque headwall outlined in blue. The steep upper paret of the headwall is shown with closely spaced contour lines indicating a rapid change in elevation over a short distance. Moving away from the head wall, the contour lines become more evenly spaced indicating the flatter surface of the cirque floor. The rock glaciers can be seen as rather evenly spaced contours that bulge outward, in the vicinity of the letters "RG". |
Figure
7.4 Pawnee Cirque as depicted on portions of Monarch Lake and Ward topographic maps