Feature Fact File: Eskers
What exactly is an esker?
An esker is a narrow ridge of stratified sediment, meaning that it is well sorted and has layers. The reason it is well sorted is due to the fact that the sediment used to be carried in a stream of meltwater. Eskers have steep sides and can be up to 500 miles (but not continuous) long. They are not usually more than 1000 feet wide and 150 feet tall.
How do eskers form?
Eskers form when streams of glacial meltwater form tunnels underneath the glacier. These streams transport sediment that the meltwater picks up down is tunnel. Over time, this sediment is deposited in the streambed and eventually the tunnel will be completely filled. When the glacier retreats, the sediment remains in the ridge-like shape of the ice tunnel that it once filled.
|As shown here, eskers form when ice tunnels get clogged with sediment, leaving a ridge behind when the glacier retreats.|
Where do eskers form?
Well, we kind of just talked about how they eskers form in these ice tunnels. The tunnels themselves are typically located in the ground moraine of a continental glacier.
Other interesting facts:
Due to their long winding shape, many roads are built on top of eskers.
Have a fantastic day!
An esker. Digital image. NE Geology Kids. OneGeology, n.d. Web. 25 May 2013. <http://www.onegeology.org/extra/kids/images/P219697esker.jpg>.
Formation of an esker. Digital image. North Dakota. North Dakota Geological Survey, 29 Aug. 2007. Web. 25 May 2013. <https://www.dmr.nd.gov/ndgs/ndnotes/Eskers/images/esker%20formed%20copy.jpg>.