Sometimes a stream cuts a channel under a slow-moving glacier, creating a long, winding ridge of sand and gravel that is called an esker. Before the glacier melted, the banks of these streams were defined by glacier ice. The deposited gravel now stands high above the surrounding land.

An esker is an attractive landform formed through fluvioglacial deposition. It is a winding ridge of low-lying stratified sand or gravel dominating the terrain and providing the vintage point and dry routes. An esker occurs in a glaciated area or a formerly glaciated region, especially in Europe and North America. The esker lies on valley floor within the ice margins marked by a moraine system suggesting that the eskers are formed beneath the glacier. The word esker is an Irish word meaning a ridge or an elevation which separates two plains. The term is also used to refer to ridges which are deposits of fluvioglacial material. Eskers vary in size and shapes with most of them being sinuous. The longest eskers are continuous and measure few kilometers while most of them are short and discontinuous.

Eskers are formed on washed sands and gravel. Most eskers are formed within ice-walled tunnel by streams which flow under and within glaciers. When the ice wall melts away, water deposits remain as winding ridges. Eskers can also be formed above the glacier through the accumulation of sediments in supraglacial channels. Eskers are formed at the terminal zones of glaciers where the ice is flowing relatively slowly. The melt water collects and flows through a network of tunnels. This water carries highly charged with debris which is composed of coarse-grained gravel which are stratified and sorted. The shape and size of the subglacial tunnel are determined by the flow and melting of the ice. The form of the tunnel then determines the shape and structure of an esker.

Credit: World Atlas

Picture Credit : Google

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