Drumlin
Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 11, Ch 6 "Landforms and their Evolution"
Meaning
A drumlin is a smooth, oval hill made mostly of glacial till, which is the unsorted mix of rock and mud that glacier ice drops. It can be up to about 1 km long and about 30 m high. It forms under a moving glacier, which moulds the till into a streamlined shape. Its long axis lies parallel to the direction the ice moved. The blunt, steep end, called the stoss end, faces up-glacier. The gentle tail points down-glacier. So a drumlin works like a compass that shows which way the old ice flowed.
Example
Clew Bay in western Ireland has many drumlins. The sea later drowned them, so they now stand as small, rounded islands. The ice sheet that shaped them during the last Ice Age is long gone.
Don't confuse with
- Esker: an esker is a long, winding ridge of gravel laid down by meltwater streams. A drumlin is a short, oval hill of unsorted till shaped by the ice itself.
- Roche moutonnée: this is a hill of bare rock with a gentle up-glacier side and a steep, plucked down-glacier side. On a drumlin the steep end faces the other way, up-glacier.
Related concepts
- Glacial till
- Outwash deposit
- Moraine
- Terminal moraine
- Lateral moraine
- Medial moraine
- Esker
- Outwash plain