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

The topographic map below has a good example of a glacial trough, or U-shaped valley. The bottom of the valley is relatively flat, shown by the wide spacing of the contour lines. The contour lines displaying the valley walls are much closer together indicating much steeper slopes. On the bottom of the valley is a stream as well as some paternoster lakes (Snow Lakes).

Topographic map: Mount Abbot, CA

The photo below shows a classic example of a glacial trough or U-shaped valley. The bottom of the valley is wide and relatively flat and the river does not appear large enough to have carved out such a large valley. Glaciers not only change the cross-profile of alpine valleys from V-shaped to U-shaped, they also tend to straighten the valleys. The Jollie River Valley is quite straight. It would be uncommon for an alpine river to carve out such a straight valley for this long of a distance.

Photo: u-shaped valley/glacial trough

Photo: T. Detwyler. Used with permission.

The photo to the right shows a u-shaped valley/glacial trough and the Noatak River. Although no glaciers fill this portion of the valley, the broad relatively flat floor of the valley and the relatively straight path of the valley indicate a glacier shaped the valley, not the Noatak River.



Photo: u-shaped valley/glacial trough

Photo: U.S. Fish and Wildlife Service National Digital Library. 2008. image Volume1\138B220F-1143-3066-40A8372CE4D026CD.jpg. <http://www.fws.gov/digitalmedia> Accessed June 2010.

Topographic map: U-shaped valley/glacial trough The long U-shaped valley/glacial trough shown on the topographic map to the right is outlined in turquoise. The source cirques for the glacier that carved this valley are partly cut off the bottom of the map. The wider spacing of the contour lines along the valley floor indicate a relatively flat topography compared to the valley walls. The river flowing along the bottom of the valley is most likely too small to have carved such a wide valley. In addition, at the elevations shown on the map (over 10,000 feet above sea level) rivers will carve out V-shaped valleys. Due to the shape of the valley and its relatively straight path, and the presence of cirques in the region, you can deduce that the valley was most likely carved by a glacier not a river.

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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 June 2010 KAL.