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 up-ice direction.
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The 18th-century Alpine explorer Horace-Bénédict de Saussure coined the term 'roches moutonnées' in 1786. He saw in these rocks a resemblance to the wigs that were fashionable amongst French gentry in his era and which were smoothed over with mutton fat (hence 'moutonnée') so as to keep the hair in place.[1]
The appearance of the erosional stoss and lee feature is very defined on Roche moutonnée as all the sides and edges have been smoothed and eroded in the direction that the glacier that once passed over it. It is often marked with glacial striations.
The rough and craggy down-ice side is formed by "plucking", the erosional process in which ice melts slightly by pressure and seeps into cracks in the rock. When the water refreezes, the rock becomes attached to the glacier. But as the glacier continues its forward progress it subjects the stone to frost shattering ripping strips away from the rock formation.
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.
Media related to [//commons.wikimedia.org/wiki/Category:Roches_moutonn%C3%A9es Roches moutonnées] at Wikimedia Commons
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