Title Bar: Illustrated Glossary of Alpine Glacial Landforms

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    Erosional Landforms
    Giant stair steps
    Glacial trough
    Hanging valley
    Paternoster lakes
    U-shaped valley

    Depositional Landforms
    End moraine
    Ground moraine
    Lateral moraine
    Medial moraine

    Ice Features
    Cirque glacier
    Valley glacier
    Ice fall

Topographic map: cirque

The topographic map to the left shows two excellent examples of cirques; a solid red line identifies their headwalls. Both cirques still contain glaciers, which are symbolized by blue contour lines on a white background with a dashed blue line marking the edge of the glaciers. Both glaciers were larger in the past than they were at the time of map creation. Clues that indicate their former size include moraine deposits, shown as brown speckles, that extend well beyond the glacier termini, particularly with the northern of the two glaciers. In addition, U-shaped valleys extend down-valley from the glaciers and only glaciers, not rivers, carve out U-shaped valleys at high altitudes.

Clues that indicate these are cirques include the approximately semi-circular shape of the contour lines, the close spacing of the contour lines on the cirque headwalls, the presence of glaciers in the cirques, and the fact that the top of the cirque headwall is at the top of a ridge - there is no place higher to go once you reach the top of the cirque headwall.

Can you find another example of a cirque on this map?

Topographic map: cirque

This second topographic map contains multiple cirques identified by a solid red line. Some of these cirques still contain remnants of the glaciers that carved the cirques, while other cirques have no ice left, just tarns (glacial lakes). Note that the cirques are not all the same size or the same shape, but they are all approximately semi-circular and they all have steep headwalls. Tulainyo Lake sits at the bottom of a cirque although the headwall of that cirque is not marked with a solid red line as the other cirques are.

Other glacial landforms in addition to cirques and tarns include horns, aretes, and moraines. The horns are pyramid-shaped mountain peaks with three or four glaciers eroding away on different sides of the horn. The moraines are symbolized as brown speckles. The aretes are not labeled but they are the ridges that define the borders of the cirques. For example, the ridge separating the cirque containing Iceberg Lake from the neighboring cirque to the west is an arete. Likewise the ridge top that separates the cirque containing Tulainyo Lake from the cirques to the east is also a tarn.

The bedrock defining the cirque in the photo below has a classic semi-circular shape.

Photo: cirque

The semi-circular shape of the cirque in the photo below is quite obvious (red line). The glacier is flowing out of the cirque toward the bottom of the photo.

Photo: cirque

Above Photo: J.A. Hyatt. Used with permission.



Left Photo: A. Post. 1966. USGS Photographic Library, photo post00008. < http://libraryphoto.cr.usgs.gov/> Accessed June 2010.

Open this link to see a photo of the landscape diagrammed below.

Diagram: cirques, aretes, horns There are three excellent examples of cirques separated by aretes in this photo. The fourth and left-most cirque is partly cut off. The cirques are the bedrock features that hold the glaciers. Once again note that the cirques are not all the same shape but they are all approximately semi-circular in shape with steep headwalls, and they are all located at the head of the valleys that were once filled with glacial ice.
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All commercial rights reserved. Copyright 2010 by Karen A. Lemke. Earlier copyright 2002 by Karen A. Lemke, and 1998 by Karen A. Lemke and Linda Freeman.
Last updated July 2010 KAL.