November 23, 2012

Geology Word of the Week: D is for Drumlin

Posted by Evelyn Mervine

Geologist Liz Johnson in front of drumlins in Clew Bay, Ireland. Picture courtesy of Liz Johnson.

def. Drumlin:
An elongated hill or ridge with a shape resembling an upside-down spoon or a half-buried egg that was formed out of glacial till– and sometimes other material such as gravel and even bedrock– that was shaped by the movement of a glacier. A drumlin carved in bedrock is usually called a “rock drumlin.” Drumlins have a steeper end and a less-steep, more tapered end. The shape of a drumlin gives an indication of ice flow in the glacier or ice sheet that formed it. The steeper end of a drumlin was formed upstream and the more tapered end was formed downstream in the ice flow. Drumlins, like many features carved by glaciers, generally appear in groups. So, it is not uncommon to find fields of drumlins.

Another view of the drumlins in Clew Bay, Ireland. Picture courtesy of Liz Johnson.

A drumlin at Drumlins Golf Course in Syracuse, New York. Picture courtesy of Tannis McCartney.

Drumlin field south of Lake Ontario (the large bay in the upper left that is not colored blue is Irondequoit Bay near Rochester, NY). Map made in GeoMapApp and courtesy of Tannis McCartney.

If anyone else has good drumlin pictures, please send them to me, and I’ll add them to this post. My fellow AGU blogger Callan Bentley also has a couple of posts about drumlins:

Drumlin Land
Litter of Drumlins

***Thanks to my friend Joy for suggesting this week’s word and to Liz Johnson and Tannis McCartney for providing pictures.***