They typically form when erosion of slopes beneath a bergschrund results in mass wasting, and the freeze-thaw cycle commonly causes their headwalls to retreat, resulting in avalanches.
During early stages of their formation, their development may be traced by a radial series of deep depressions which become partially flooded downstream from their source in the final stage, forming paternoster lakes. The encroachment of three of them upon one point creates a nunatak, and when two of them grow together, they erode away their restraining ridges, or ar?es [uh-rehts], and ultimately merge, forming a col. They typically form when erosion of slopes beneath a bergschrund results in mass wasting, and the freeze-thaw cycle commonly causes their headwalls to retreat, resulting in avalanches. In warmer months, they often fill with water, creating lakes called tarns. FTP, name these steep, concave downward basins found at the heads of glacial valleys.
During early stages of their formation, their development may be traced by a radial series of deep depressions which become partially flooded downstream from their source in the final stage, forming paternoster lakes.
cirque basins or corries