Arête

An arête is a thin, almost knife-like, ridge of rock which is typically formed when two glaciers erode parallel U-shaped valleys. The arête is a thin ridge of rock that is left separating the two valleys. Arêtes can also form when two glacial cirques erode headwards towards one another, although frequently this results in a saddle-shaped pass, called a col. The edge is then sharpened by freeze-thaw weathering, and the slope on either side of the arete steepened through mass wasting events and the erosion of exposed, unstable rock.^[2] The word "arête" is actually French for edge or ridge; similar features in the Alps are described with the German equivalent term Grat.

• http://en.wikipedia.org/wiki/Arête