In researching glacial features, I came across the terms esker, drumlin, and kame. I know that they are all depositional features that are shaped like a mound. My impression is that an esker is longer than a drumlin, which is longer than a kame. What other differences distinguish between the three?
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3 Answers
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Eskers are glaciofluvial deposits from sediment carrying subglacial tunnels. As the water emerges from a tunnel at the bed of an ice sheet or glacier it will slow down. Since the sediment movement depends on water velocity the sediment will be deposited. The results is a highly localised deposition. When glaciers retreat the point of emergence for the water will of course change with the edge of the glacier. Hence the deposition will occur progressively further upstream leaving a narrow trail of sediment accumulation. Much more can be said but the result is ridges sometimes hundreds of kilometres long that extend pretty much perpendicular to the past glacier edge, the way the water flows from within to the edge of the glacier.
Kames are hummocky terrain formed by material that has been transported by glacier melt water. The reasons for the hummocks is that when the sediment was deposited, chunks of ice were buried by the sediments and when that ice melted a hummocky terrain was formed. A key here is that the deposition of sediments from sediment transport would not be able to form the irregular hummocky terrain as a primary feature, there has to be other processes involved. Kames are therefore usually an extensive land form that does not necessarily have a preferred extension. As with eskers the origin of the water and sediment is the same, the base of the glacier.
Finally, drumlins. These forms are elongated land forms, in the direction of ice flow, often some kilometres in length, width of a few hundred metres and a height of tens of metres. This varies a lot though. These forms are not formed by running water and sediment transport but formed beneath the ice. In the literature they have been described as both depositional and erosional land forms, although a depositional formation seems to be most common. They seem to consist of whatever material is present beneath the ice but because the most common sediment beneath glaciers is till this is also what most drumlins consist of.
So eskers and kames have som relationship in the origin of the sediment that make them up. Drumlins are of completely different processes. Much more could be said and all details are not completely understood when it comes to many glacial landforms and their formation.
ADDED: The formation of drumlins, and hence also their characteristics is too complex to be explained in a short answer here. Three scientific papers that will help gaining a deeper understanding of drumlin formation are (I suggest googling on the titles to find copies):
Patterson, C.J., Hooke, R.L., 1995. Physical environment of drumlin formation. Journal of Glaciology 41 (137), 30��38.
Stokes, C.R., Spagnolo, M., Clark, C.D., 2011. The composition and internal structure of drumlins: complexity, commonality, and implications for a unifying theory of their formation. Earth-Science Reviews 107, 398–422.
Roger LeB. Hooke, Aaron Medford, 2013. Are drumlins a product of a thermo-mechanical instability? Quaternary Research. http://dx.doi.org/10.1016/j.yqres.2012.12.002
answered Apr 18, 2017 at 21:38
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1$\begingroup$ Some drumlins are much smaller than you described - maybe only 30 m or so wide and can be quite a bit shorter. I wouldn't say till is the most common sediment beneath glaciers, though. For example much of northern Canada is exposed bedrock and drumlins then can be made up of very locally derived ripped up sedimentary rock and generally do not form to the same degree on harder crystalline basement. $\endgroup$– haresfurCommented Apr 19, 2017 at 22:17
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1$\begingroup$ Well that is what is meant by "This varies a lot though" $\endgroup$ Commented Apr 20, 2017 at 7:45
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$\begingroup$ They are all depositional features, though, correct? $\endgroup$ Commented Apr 20, 2017 at 22:33
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$\begingroup$ The intraglacial streams themselves are called eskers (at least, my old geomorph textbook does) and there is often intraglacial sediment deposition, especially bed load. $\endgroup$– SpencerCommented Apr 14, 2020 at 13:18
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1$\begingroup$ This definition of esker is incorrect according to my understanding and the link in the answer by @cat. Eskers are sub-glacial deposits and not formed only at the location where the tunnel emerges. If they were outwash features they would not stand as high above the surrounding land surface $\endgroup$– haresfurCommented Apr 15, 2020 at 4:08
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I was personally looking for an answer to this question as well, and I found these sites very helpful.
The National Park Service Website:
- Drumlins: https://www.nps.gov/articles/drumlins.htm
- Eskers: https://www.nps.gov/articles/outwashplainsandeskers.htm
And Landforms.Eu:
GEOL100:
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4$\begingroup$ If you wouldn't mind, what did you find useful/what did you learn? Links are certainly very good, but always nice when we can pare down an answer and put it here, where we shouldn't have to worry about links dying. $\endgroup$ Commented Feb 4, 2018 at 2:06
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Drumlins: elongated egg-shaped hills
Kames: dumpling shaped hills
Eskers: long sinuous hills, snake shaped
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$\begingroup$ Eskers are often linear, not sinuous. Linear eskers are common in northern Canada. I can't recall having seen meanders in eskers, but maybe they occur. $\endgroup$– haresfurCommented Apr 15, 2020 at 4:11