Roche moutonnée

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Roche moutonnée landform in the Cascade Mountains near Cle Elum, Washington. Direction of glacier movement is from right to left.

In glaciology, a roche moutonnée (or sheepback) is a rock formation created by the passing of a glacier. When a glacier erodes down to bedrock, it can form tear-drop shaped hills that taper in the direction of flow.

The appearance of the erosional glacier feature is very defined: a rock formation where all the sides and edges have been smoothed and eroded in the direction of the glacier that once passed over it, with the exception of the rough and craggy opposite side. It is this side that has been subjected to "plucking", the erosional process in which ice melts slightly by pressure and seeps into cracks in the rock. When the water freezes, the rock is attached to the glacier and eventually ripped away from the landform as the glacier continues its forward progress. It is also subjected to frost shattering.

The term "roche moutonnée" comes from the French for "fleecy rock", despite its popular misinterpretation as "rock sheep". They are often marked with glacial striations.

Note that the side profile of a roche moutonnée is opposite to that of a drumlin. In a drumlin, the steep side is facing the approaching glacier, rather than trailing it.

[edit] See also

Glacial landforms

[edit] References

Tarbuck, E.J.; F.K. Lutgens (2002). Earth: An Introduction to Physical Geography, 7th ed.. Upper Saddle River, NJ: Prentice Hall, 342. ISBN 0-13-092025-8.
Trenhaile, Alan (2007). Geomorphology: A Canadian Perspective. Don Mills, Ontario: Oxford University Press, 180-1. ISBN 0-19-542474-3.