Giant stair steps
| A steep-sided, sharp-edged bedrock ridge formed by two glaciers eroding away on opposite sides of the ridge.
Photo: K.A. Lemke (used with permission).
Mt. Oberlin (to the left of the waterfall in the photo) in Glacier National Park is an example of an arete. In the photo you
are looking toward the southeast. On the map, north is toward the top. The photo was taken from Going to the Sun Highway
shown in red on the map where the camera is located. The waterfall is labeled on the map, as is Mount Oberlin. On the map, the arete
is shown by elongate closed contour lines that are very closely spaced. The close spacing of the contour lines reveals the steep
sides of the arete. Two glaciers shaped this arete by eroding away at opposite sides of Mt. Oberlin. One glacier flowed in the
valley currently occupied by Logan Creek and the other glacier flowed north along the unnamed stream where the waterfall is. Thus one
thing to look for when identifying aretes is the existence of glacial troughs on either side of the arete. Aretes may also form between
two cirques, in which case two cirque glaciers will erode away on opposite sides of the ridge, not two valley glaciers.