Related Glacial Structures
Corrie glaciation, although small, is a complex process of accumulation, ablation, and erosion. As glaciers grow, they grind away at the mountain creating not only cirques, but also a variety of glacial formations. When two cirques form on opposite sides of a ridge, they erode it down to a knife edge, creating the landform known as an arête. When multiple cirques or mountain glaciers erode all sides of a mountain they form a horn. A famous example is the Matterhorn. The above (right) image shows the glacial horn, Mount Stimson, in Glacier National Park, Montana. An arête extends to the left of the horn and three cirques are visible below.
Sometimes cirques fill with water creating tarn lakes. A series of tarns stepping down the valley are paternoster lakes. These lakes connect with a single narrow stream, giving the effect of beads on a string. Although they may begin in cirques, paternosters typically form beneath valley glaciers when the valley floor erodes unevenly due to varying rock types. Harder materials are more resistant to the glacier’s forces and softer materials give way more easily. As in washboard ripples or potholes in roads, the depressions grow over time. Ridges of glacial deposits also form dams along the valley floor to create paternoster lakes.
As glaciers grow, they pick up and carry debris from the mountain. This poorly sorted glacial sediment known as till is deposited to form moraines when glaciers recede. Moraines are found in cirques as well as valleys and come in lateral, medial, ground, and terminal varieties, depending on their orientation and position in relation to the glacier.