Water Movement within the Glacier System
– Glacier hydrology is the study of the flow of water through glaciers.
– Water running on the surface of the glacier can disappear through cracks and holes in the glaciers and powerful rivers can later emerge from the glacier snout.
– Beneath the Antarctic Ice Sheet, these subglacial drainage channels are connected to numerous subglacial lakes.
Supraglacial Hydrology
– Supraglacial water on a glacier is formed by the ice melting during the summer.
– It flows off the glacier, incising a number of cracks similar to an ordinary river system.
– Surface melt (ablation) occurs in the hard-packed snow (firn; the transitional state between snow and ice) and can pond above the impermeable ice.
– This process undergoes seasonal change.
Englacial Hydrology
– Structures in the ice, such as crevasses, allow the water to penetrate into the ice.
– There are some great examples of this in Greenland, where large lakes can abruptly drain into the ice sheet.
– Moulins are vertical shafts cut by the water.
– Despite the pressures within the ice sheet, moulins remain open by constant melting by the water.
– Finally, there are numerous water pockets and channels within temperate ice sheets and glaciers, where water can remain trapped for some time.
Subglacial Hydrology
– Subglacial hydrology is critically important in understanding the flow of glaciers.
– Basal meltwater flows through large subglacial hydrological networks, which can impact glacial erosion and ice velocity.
– Some of these channels can be followed for hundreds of kilometres (in Antarctica).
– There is evidence that this hydrological system is very variable
– Changes within the glacier bed have been observed underneath Antarctic ice.
Fluvioglacial Landforms
The term fluvioglacial refers to glacial meltwater.
You need to be able to explain the difference between fluvioglacial and glacial deposits. Fluvioglacial are:
– Smaller: in terms of total amount (volume) of deposit
– More Rounded: due to hydrological processes (attrition)
– Sorted Horizontally: in the case of outwash material, the largest is found up-valley (near the snout), and progressively finer material down-valley
– Stratified Vertically: layers reflect seasonal or annual accumulation
Fluvioglacial Landforms
