Paysage glaciaire

Glacial landforms are landforms created by the action of glaciers. Most of today's glacial landforms were created by the movement of large ice sheets during the Quaternary glaciations. Some areas, like Fennoscandia and the southern Andes, have extensive occurrences of glacial landforms; other areas, such as the Sahara, display rare and very old fossil glacial landforms. As the glaciers expand, due to their accumulating weight of snow and ice they crush, abrade, and scour surfaces such as rocks and bedrock. The resulting erosional landforms include striations, cirques, glacial horns, arêtes, trim lines, U-shaped valleys, roches moutonnées, overdeepenings and hanging valleys. Striations: grooves and indentations in rock outcrops, formed by the scraping of small sediments on the bottom of a glacier across the Earth's surface. The direction of striations display the direction the glacier was moving. Cirque: Starting location for mountain glaciers, leaving behind a bowl shaped indentation in the mountain side once the small glacier has melted.(add geology book citation already in the article) Cirque stairway: a sequence of cirques U-shaped, or trough, valley: U-shaped valleys are created by mountain glaciers. When filled with ocean water so as to create an inlet, these valleys are called fjords. Arête: spiky high land between two glaciers. If the glacial action erodes through, a spillway (or col) forms Horn: a sharp peak connecting multiple glacier intersections, made up of multiple arêtes. Valley step: an abrupt change in the longitudinal slope of a glacial valley Hanging Valleys: Formed by glacial meltwater eroding the land partially, often accompanied by a waterfall. Later, when the glaciers retreated leaving behind their freight of crushed rock and sand (glacial drift), they created characteristic depositional landforms. Depositional landforms are often made of glacial till, which is compiled of unsorted sediments (some quite large, others small) that were eroded, carried, and deposited by the glacier some distance away from their original rock source.