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The height and width of an esker are determined by the water and ice pressure and sediment load at the time of formation. [36] Eskers form in ice tunnels within or under a glacier, as shown in Figure 1, and are composed of the sediment deposits from the streams that occupy these tunnels. [37]
Glaciers erode and deposit sediment by advancing and retreating. [4] Erosion occurs by abrasion and plucking. [4] These processes are dependent on a variety of factors such as plate tectonic movement, volcanic activity, and changes in atmospheric gas composition. [5]
Sediments deposited into lakes that have come from glaciers are called glaciolacustrine deposits. In some European geological traditions, the term limnoglacial is used. These lakes include ice margin lakes or other types formed from glacial erosion or deposition. Sediments in the bedload and suspended load are carried into lakes and deposited ...
Fluvioglacial deposits differ from glacial till in that they were deposited by means of water, rather than the glacial itself, and the sediments are thus also more size sorted than glacial till is. The stone walls of New England contain many glacial erratics, rocks that were dragged by a glacier many miles from their bedrock origin.
Subglacial streams can transport, deposit, and remove sediment from the glacier bed; this process is influenced by water supply and the amount and characteristics of the available sediment. [12] The size of sediment particles, the slope of the subglacial stream’s channel, and the roughness of the bed all contribute to whether sediment is ...
The sediments carried by a glacier will eventually be deposited some distance down-ice from its source. This takes place in the ablation zone , which is the part of the glacier where the rate of ablation (removal of ice by evaporation, melting, or other processes) exceeds the rate of accumulation of new ice from snowfall.
Glaciers also pulverize rock into "glacial flour", which is so fine that it is often carried away by winds to create loess deposits thousands of kilometres afield. Sediment entrained in glaciers often moves approximately along the glacial flowlines, causing it to appear at the surface in the ablation zone.
Drift is often subdivided into unstratified (unsorted) drift (glacial till) that forms moraines and stratified drift (glaciolacustrine and fluvioglacial sediments) that accumulates as stratified and sorted sediments in the form of outwash plains, eskers, kames, varves, and so forth. The term drift clay is a synonym for boulder clay. Both are ...