Glacial processes
Phenomena
Hummocky moraine (Svalbard) – Ground moraine with undulated surface. Relief consisting of steep slopes, ridges, channels and deep depressions filled with meltwater. Local relief of <10 m. Hummocky moraine is a result of thinning of glacial terminus. Ice squeeze the debris from the melting ice into the creavasses between ice blocks – these infilled crevasses forms the ridges and hummocks after complete melting of ice (inverted topography).
Englacial egg gravel (Svalbard) – note the different roundness of gravel near the feet of the man on the picture. Egg gravel is a result of transport of gravel through the supraglacial (on-the-top-of-glacier) and englacial (inside-the-glacier) streams and channels (tunnels). Clasts are worked during the transport. Clasts can be preserved in the channel dead-ends and can infill crevasses as well. After the glaciet retreat they are deposited as a pile of rounded clasts between angular and semi-worked clasts.
Kettle lake (Svalbard) – forms from the in-situ melted block of dead-ice. Note the glacier terminus in the left.
Esker (Svalbard) – elongated elevation formed by gravel and sand originally transported through the englacial and subglacial (under-the-glacier) streams (tunnels). After glacier retreat this channel infill is preserved as a long, winding elevation. Because of their shape, they somehow look like a railway embankment.
Climbing moraine (Svalbard) – moraine was originally lying on the top of glacier. The moraine “climbs” up the sticking-up rocks with the glacier retreat and thinning.
Supraglacial stream (Svalbard) – stream flowing on the top of glacier, forming narrow and deep channels. The stream carries the clasts that can infill ice cracks, depressions and crevasses. These deposits form the hummocky moraines after the glacier retreat. Two roche moutoneés (sheepbacks) can be seen in the background.
Medial moraine (Svalbard) – the ridge that runs down the centre of valley. It forms when two glaciers merge and their side moraines join and the resultant medial moraine is carried on the top of merged glacier.
Glacial striation (Svalbard) – scratches that are cut into bedrock by glacial abrasion. You can see two directions of scratches on this particular bedrock outcrop. Change of direction is caused by the local topography and change of glacier flow direction after its partial retreat.
Roche mountoneé - sheepback (Svalbard) – rock formation created by passing glacier. The direction of glacier flow was from right to the left. The stoss (upper) side is formed by ablation and is smooth and gentle-sloping with abundant glacial striation. The lee (down-ice) side is rough and formed by quarrying and plucking of ice.
GLOF (Svalbard) – glacial lake outburst flood. GLOF is a process that occurs when the dam holding the glacial meltwater is breached. Huge amount of water than rapidly flows through unconsolidated proglacial tills. GLOF can create huge channels like the one on the picture.
Hanging glacier (Svalbard) – hanging glacier is glacier whose base is substantially higher than the base of the main valley. The hanging glacier is usually abruptly terminated by a cliff. Two roche moutoneés can be seen in front of the hanging glacier. During LIA (Little Ice Age) these elevations were under the glacier.
Rock tower (Torres del Paine, Chile) – Deeply eroded rock body with a tower-like shape. They can be created in varied rock types and can be a result of different erosional processes (glacier, marine etc.). Summits of Torres del Paine are granite monoliths (laccolith) intruded in older sedimentary rocks (flysh deposits) and subsequently shaped by glacial erosion.
Glacier table (Aletschgletscher, the Alps, Switzerland) – A boulder transported on the top of a glacier and perched on an ice pedestal. The ablation of the ice under the boulder is reduced.
Striation/striae (Torres del Paine, Chile) – Linear scratches formed by the glacier abrasion. Striae are formed when basal debris-rich ice is sliding over the bedrock.
Hanging glacier (Colgante glacier, Quelat National Park, Chile) – A glacier that is located in a high-elevated cirque or lies high on a steep mountainside. The melting water of hanging glacier could create waterfalls.
Horn (Matterhorn, the Alps, Switzerland/Italy) – A steep-sided, pyramid-shape peak which was formed as a result of the backward erosion of cirque glaciers from three or more sides.
Nunatak (Grey glacier, Torres del Paine National Park, Chile) – Isolated peak (island of bedrock) protruding above the surface of a glacier or an ice sheet.
Erratic (Beisfjord, Narvik, Norway) – A boulder carried away from its source area by a glacier. It differs from the type of surrounding rocks and can be transported over the distance of hundreds of kilometres.
Erratic (Lyme Park, Derbyshire, UK) – A boulder carried away from its source area by a glacier. It differs from the type of surrounding rocks and can be transported over the distance of hundreds of kilometres.