Esker
Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 11, Ch 6 "Landforms and their Evolution"
Meaning
An esker is a long, narrow, winding ridge of coarse sand, gravel and boulders. Meltwater streams lay it down while flowing in tunnels under or inside a glacier. The tunnel walls are made of ice, so the stream drops its load in a long line along the tunnel floor. When the ice melts, the line of sediment is left standing as a snake-like ridge. Because running water laid it down, an esker is roughly sorted and layered, unlike till. Eskers show where meltwater flowed beneath the old ice.
Example
The Esker Riada is a chain of eskers that runs across central Ireland. For centuries people used its dry, raised ridges as a natural road across low, boggy land.
Don't confuse with
- Drumlin: a drumlin is a short, oval hill of unsorted till shaped by moving ice. An esker is a long, winding ridge of sorted gravel laid by meltwater.
- Moraine: a moraine is till dropped directly by ice. It is unsorted and angular, while an esker is water-laid and roughly sorted.
Related concepts
- Glacial till
- Outwash deposit
- Moraine
- Terminal moraine
- Lateral moraine
- Medial moraine
- Outwash plain
- Drumlin