We went looking for one of Trail Magazine's Marv the Marmot mascots as part of their Everest Anywhere campaign. http://www.livefortheoutdoors.com/everestanywhere/ We found it hidden at the Y Boulder in Mosedale near Wasdale Head. I'd never heard of this remarkable rock but it is a named feature on the OS map. So how did it end up with a Y shaped crack in it? At first I thought it must be a glacial erratic. Mosedale is a classic hanging valley carved out by a tributary glacier. It is U-shaped in section and there is a waterfall at the end down into the main valley. Glaciers pick up and deposit rocks. But this rock is very square edged. That doesn't sit well with transport. We looked at the slope around and above. Scree above is created by freeze-thaw cycles. Solid H20 takes up more space than liquid because the bond angles force it open. Thus freezing of water in cracks tries to push rock apart. I didn't think lumps this big fell off crags but then I remembered that there is a lump said to be the size of a bungalow about to fall from Castle Rock of Triermain. My guess is that this rock fell from the crag above and cracked for that reason.
