August 1996
Supraglacial moraine is material on the surface of the glacier, including lateral and medial moraine, loose rock debris and dust settling out from the atmosphere. .
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| Material can be carried on top of the ice (supraglacial). Rocks can be weathered by freeze thaw weathering action (for example) and fall on to a glacier becoming its load. The glacier erodes it and carries it away. The material at the edge of a glacier is called a lateral moraine. | |
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This photo shows a medial
moraine formed where two tributary glaciers have joined together
into one bigger glacier. Two lateral moraines therefore meet and a
medial moraine is formed in the middle of the glacier. Notice
how massive one boulder is and compare it to the helicopter!Herbert
Glacier, Southwest Alaska August 1996 |
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| This photo shows two
medial moraines (blue arrows) as seen from the air. The black arrows point
to lateral
moraines that have formed along the sides of the valley wall. Where
the two main glaciers shown in the photo flow together, their lateral
moraines join to form a medial moraine. The medial moraine on the right
formed in the same way, however we can't see where the glaciers flow
together to form the moraine. The moraines lie on top of the ice - supraglacial
Supraglacial moraine is material on the surface of the glacier, including lateral and medial moraine, loose rock debris and dust settling out from the atmosphere. . |
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Englacial moraine is any material trapped within the ice. It includes material that has fallen down crevasses and the rocks being scraped along the valley floor.The photo shows supraglacial moraine falling down a crevasse and becoming englacial moraine | |
| Subglacial moraine mostly debris plucked from the bed and embedded in the ice. It is carried at the base of the glacier and can then help to further erode the valley floor by abrasion. | |
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Fluvioglacial processes: Streams run as meltwater from the ends of glaciers and also run under and within the glacier. In this photograph eltwater emerges to form a new river at the exit of a glacier near Seward, Alaska The meltwater can carry away material as any river would do hence the term fluvioglacial. | |
| The rocks that have been recently melted out of the glacier have all different sizes mixed together. This is called "unsorted till." Over many hundreds of years, the unsorted till will be pushed and carried by streams until much of it is sorted out into patches of different sizes. An important point here is that material deposited by glaciers is usually unsorted i.e. like 'boulder clay' a range of sizes from boulders to clay but river deposited sediment is usually graded or sorted - at high energy times only heavy particles will be deposited at times o low energy finer material may be deposited. Large grains might be deposited nearer the snout of the glacier and finer material might have been washed much further away. | |
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In the photograph these scientists are standing on a bluff about 60 meters above the valley of the Matanuska River, The bluff mostly consists of silt deposited by rivers from glaciers which melted many thousands of years ago. New glaciers formed, and as the more recent glaciers have melted, the water from their melting has cut through the ancient silt deposits and formed a valley about 1 to 2 kilometers wide, with a flat bottom. On the bottom of the valley the outwash stream from the glacier splits into many small streams which wash over the rock deposits, sorting them into deposits of different sizes. This is a landform of glacial deposition. It also shows modification of glacial landforms by other geomorphological processes - Key Idea 3b) | |