Valley shoulder

Schematic cross section of an quarterny Alpine valley. In the Eastern Alps the valley's shoulders often coincide with the upper limit of the winter inversion's fog

A glaciated valley in the Mount Hood Wilderness showing a characteristic U-shape and the broad shoulders

In Geomorphology the Valley shoulders are the protruding structures of the valley slopes which are approx. parallel to the valley axis. They characterize the profile across valley, together with the valley floor and the slope inclination.

In high mountain regions like the Alps but also in Scotland, Scandinavia, New Zealand or Canada, many valleys and dales are U-shaped. This landform with steep, straight sides and a flat valley bottom is mostly formed by the process of glaciation during the ice age and therefore is called "glaciated valley", too. The shoulders of U valleys are often located approximately halfway up the slopes. Usually this indicates the maximum elevation of glacial erosion (see top figure).

The broader a mountain valley, the lower its shoulders are located in most cases. An important exception are canyons where the shoulder almost is near the top of the valley's slope. In the Alps - e.g. the Tyrolean Inn valley - the shoulders are quite low (100-200 meters above the bottom). Many villages are located here (esp. at the sunny side) because the climate is very mild: even in winter when the valley's floor is completely filled with fog, these villages are in sunshine.

Looking from Paria View to a valley in Bryce Canyon, Utah.

For sure, such a landscape is an excellent place to live. In the book Pawky poet (last Link), this is described as follows:
On the Vermont hills about Ripton, the red fires of autumn smoldered on the swamp maples and sumac, crept inward from branch tips, inched downward into the valley where the river brawls through the gorge. From a slab-wood cabin with its back set firmly against the valley's shoulder, cooking his own meals and dependent on no man, 76-year-old Poet Robert Frost last week faced the world. It is the vantage point he likes best.

Mt.Gilbert and Right Fork Canyon, Nevada. The shoulders in the right foreground are broken by two by-valleys

In some stress-tectonic regions of the Rocky Mountains and the Alps (e.g. Salzburg) most of the side valleys are parallel to each other, and additionally they are hanging valleys. The brooks flow into the river in form of deep gorges or waterfalls. Usually this fact is the result of a violent erosion of the former valley shoulders.

Wiki and Web Links:

• glacial period, glaciated valley, Glen, Fjord, Arete (landform)
• Shoulder of the swiss Calanca valley near Braggio
• Typical valley sections (=> U valleys and terrace valleys)
• SAR interferometry (search for valley shoulders in Fig.2 and 6)
• A poet's vantage point: cabin on a valley-shoulder in Vermont

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