Nunataks, Arêtes, and Horns

A snowshoer gazes up at the jagged, glacially-carved peaks that are an important part of the landscape in Olympic National Park (Washington).

NPS Photo/B. Baccus

Nunataks, arêtes, and horns are the result of glacial erosion in areas where multiple glaciers flow. When the ice is present, they form stark, rocky outcrops above it, adding to the beauty of these harsh landscapes. Once the ice retreats, these uniquely-shaped features provide clear evidence of past glacier flow.

Nunataks

The Baldwin and Fraser Glaciers converge after flowing around a nunatak (Wrangell-St. Elias National Park, Alaska). A dark medial moraine drapes the ice surface down-glacier from the confluence.

NPS Photo/Jacob W. Frank

Nunataks are rocky islands that are surrounded by flowing glacier ice. As the glaciers surrounding a nunatak come together, a medial moraine composed of rockfall from the nunatak often marks their confluence.

Arêtes

The jagged Garden Wall of Glacier National Park (Montana) is a beautiful example of an arête that once formed a sharp, rocky crest above two of the glaciers that shaped the park. A col occurs as a rounded low point near the center of the ridgeline.

NPS Photo/Jacob W. Frank

An arête is a thin, jagged crest that separates—or that once separated—two adjacent glaciers. These rugged ridgelines often look like serrated knives or saw blades, with steep sides and a sharp crest. The low points on the serated surface are known as cols. Cols act as spillways for the ice and occur where glacier action has eroded the rock sufficiently to overtop it.

Horns

Flinsch Peak (Glacier National Park, Montana) is a beautiful example of a glacially-carved horn with its flat faces and sharp edges.

NPS Photo/Jacob W. Frank

Horns are pointed peaks that are bounded on at least three sides by glaciers. They typically have flat faces that give them a somewhat pyramidal shape and sharp, distinct edges.

To learn more about glaciers, glacier features, and glacial landforms, see the Glaciers & Glacial Landforms Page.

Related Links

• NPS—Geoscience Concepts
• NPS—Geologic Tour
• NPS—Geodiversity Atlas
• NPS—Geology