These surfaces are usually exposed above modern sea level when a heavily glaciated area experiences a glacial retreat, causing water levels to rise.
The northern region consists of an arc of glaciated mountain peaks with an arctic climate at the highest elevations.
Since the area is not believed to have been glaciated, this probably indicates that the course of the rivers pre-dates the modern topography.
The glaciated terrain in the latter makes skiing possible even in summer months.
Several deeply glaciated northeast-facing cirques are present, with steep headwalls and flats or lakes at their floors.
It is about wide and its uncovered glaciated surface is strewn with glacial erratics.
Though much of its course is marsh, it offers scenic glaciated canyons, unique ecosystems, and exceptional wild trout fisheries.
It is cut by glaciated canyons and is dotted and threaded by lakes and rushing clear streams.
