Glacier valley

Glacier valley in the natural park Posets-Maladeta (Huesca).

A glacial valley, also called a glacial trough, is defined as a valley through which a large glacier circulates or has circulated, leaving a clear geomorphology of glacierism.

Glacial valleys are rivers of ice. They are formed when the thickness of the ice accumulated in the cirque is great. Ice from the lower layers moves out of the cirque and spills down the valley. Rock fragments containing ice widen the valley. They also dig buckets in less resistant rocky areas. These basins, when the ice melts, become lakes.

Features

The glacial valleys are characterized by presenting a transversal profile in the shape of "U" or trough, considered in geomorphology the main feature that allows differentiating this type of channel through which an ice tongue slides or slipped. Other characteristics of the glacial valleys are the traces of abrasion and overexcavation caused by the friction of the ice and the dragging of material, the existence of avalanche channels, flat bottoms with alternating thresholds and basins, very vertical carved slopes that give rise to a rupture. from slope to shoulder pad and to the formation of hanging or suspended valleys.

View of the Noatak River glacier valley in Alaska.

The old glaciers gave rise to the formation of deposits of materials that had previously been eroded by the ice. These materials are very heterogeneous and often form various types of moraines (terminal, lateral, receding, etc.) in which they usually form lakes of glacial origin, such as those found on the edge of the European Alps (Como, Greater, Garda, Geneva, Konstanz, etc.) or in central Sweden and many other parts. Also, overexcavation can produce appropriate conditions for the formation of lakes of glacial origin. In the case of Venezuela, the Mucubají Lagoon is dammed by the terminal moraine of the glacier that descended in the Pleistocene from the Mucuñuque Páramo. Instead, about 2 km to the SE, the Laguna Negra is dammed by a threshold or natural dam of resistant rocks preceded by other weaker ones, which were removed by the ice of the glacier and emptied, forming what is now a deep lake..

Suspended or "hanging" valley

When the secondary glaciers converge at the bottom of the main valley through which a more important and deeper glacier moves or moved, the suspended valleys or hanging valleys are produced. Such is the case, in the Sierra de Mérida (Venezuela), of the valley where the Cascada del Sol is located: this valley descended from the Pico Bolívar but when it reached the main valley, it was excavated more than 100 meters below by the greatest amount of ice, decapitated the small glacier that now forms the suspended valley. It is a very frequent phenomenon in Argentina, Alaska, Canada, Chile, New Zealand, the Scandinavian Peninsula, Russia and, of course, in the Asian mountain ranges and in the Alps. In the case of the Norwegian fjords, the suspended valleys are a great tourist attraction, since they produce high-altitude waterfalls that fall directly into the sea inside these fjords.