Glacial landform
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.
Erosional landforms
- 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)[1]
- 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. [2]
- Roche moutonnée
- Nunatak
Depositional landforms
Later, when the glaciers retreated leaving behind their freight of crushed rock and sand (
- Esker: Built up bed of a subglacial stream, forming small, string-like mounds left behind as a glacier retreats.[1][3]
- Kame: Irregularly shaped mound of sediments perviously deposited by falling into an opening of glacial ice.
- Moraine: Built up mound of glacial till along a spot on the glacier. Feature can be terminal (at the end of a glacier, showing how far the glacier extended), lateral (along the sides of a glacier), or medial (formed by the merger of lateral moraines from contributory glaciers). Types: Pulju, Rogen, Sevetti, terminal, Veiki
- Outwash fan: Braided stream flowing from the front end of a glacier into a more flat, lower elevation plain of sediments.[1]
Glacial lakes and ponds
Lakes and ponds may also be caused by glacial movement. Kettle lakes form when a retreating glacier leaves behind an underground or surface chunk of ice that later melts to form a depression containing water. Moraine-dammed lakes occur when glacial debris dam a stream (or snow runoff). Jackson Lake and Jenny Lake in Grand Teton National Park are examples of moraine-dammed lakes, though Jackson Lake is enhanced by a man-made dam.
- Kettle lake: Depression, formed by a block of ice separated from the main glacier, in which the lake forms
- Tarn: A lake formed in a cirque by overdeepening
- Paternoster lake: A series of lakes in a glacial valley, formed when a stream is dammed by successive recessional moraines left by an advancing or retreating glacier
- Glacial lake: A lake that formed between the front of a glacier and the last recessional moraine
Ice features
Apart from the landforms left behind by glaciers, glaciers themselves are striking features of the terrain, particularly in the polar regions of Earth. Notable examples include
Disputed origin
The glacial origin of some landforms has been questioned:
Erling Lindström has advanced the thesis that
The idea of elevated
The Gulf of Bothnia and Hudson Bay, two large depressions at the centre of former ice sheets, are known to be more the result of tectonics than of any weak glacial erosion.[7]
See also
- Glacial series – Environmental Biome in Central Europe
- Nunatak – Landform within an ice field or glacier
- Pyramidal peak – Angular, sharply pointed mountainous peak
- Fluvioglacial landform
- Glaciofluvial deposits
- Limno-glacial
References
- ^ ISBN 9781591919445.
- ^ Crosby, Benjamin; Whipple, Kelin; Gasparini, Nicole; Wobus, Cameron (August 2007). "Formation of Fluvial Hanging Valleys: Theory and Simulation". Journal of Geophysical Research: Earth Surface. 112 (F3) – via AGU.
- ^ a b Eyles, Nick (August 2006). "The Role of Meltwater in Glacial Processes". Sedimentary Geology. 190 (1–4): 257–268 – via Elsevier Science Direct.
- JSTOR 521265.
- ^ .
- doi:10.1130/g34806.1.
- .
External links
- Illustrated glossary of alpine glacial landforms
- Landforms of glaciation
- Diagram illustrating mechanisms of glacial landforms in The Ice Melts: Deposition on page 6 of "Pennsylvania and the Ice Age" published 1999 by PA DCNR Bureau of Topographic and Geologic Survey[dead link]