Tuesday 23 February 2016

Low Ling Crag roche mountonee on Crummock Water

I'd been wanting to visit this feature on the far side of Crummock Water for years. Now I've been. There has been some argument on the Internet about whether it is a roche moutonee. What's the evidence? They form when a glacier goes over hard bedrock. The glacier here would have been flowing from right to left. The glacier smooths the approach side into a smooth ramp. Coming over the top, the pressure melts some of the ice which then runs into crack in the rock. This water then refreezes and gets pulled by the glacier. This rips the downstream side into a crag. Well, that seems correct with what's in the photograph. There is a diagram here https://en.wikipedia.org/wiki/Roche_moutonn%C3%A9e#/media/File:Roche_moutonn%C3%A9e_eng_text.png As to why ice melts under pressure, that's another story...