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How do glacial lakes create beach ridges and wave-cut benches?
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glacial landform
Eskers,
or narrow
ridges of
gravel and sand left by a retreating glacier,
wind through western
Nunavut, Canada, near the Thelon River.
When a glacial lake remains at a stable level for an extended period, it develops horizontal, terracelike features along its margin known as shorelines. These features are created through two primary processes:1
- Wave-cut benches: These are formed by the erosional action of waves against the bedrock or glacial sediments that make up the lake's margin.1
- Beach ridges: These are formed by the deposition of sand and gravel transported by long-shore currents along the lake's margin.1
The width of these shorelines can range from a few meters to several hundred meters. As the lake level changesâoften due to the opening of new outlets or the downcutting of spillwaysâthese shorelines may be abandoned, and new, lower ones may form. Geologists use these abandoned, often tilted shorelines to reconstruct the former size and depth of extinct or shrunken glacial lakes and to measure postglacial crustal uplift.1