April at Rhosyfelin

I spent a very pleasant Bank Holiday afternoon at Craig Rhosyfelin, "doin' a bit o' geomorfin'."  (That's how the Royal Navy personnel on HMS Protector referred to the work being done by David Sugden and myself in the South Shetlands in 1965-66.)

Plenty of images to share, and I'll probably do a number of posts about my new observations.  But to start with, here is a rather nice image of the rock face -- taken straight into a late afternoon sun.  Excellent shadows which bring out the edges of the slabs of rhyolite.  You can see the "abandoned orthostat" in its black plastic shroud, awaiting the return of the diggers in September 2014.    Not exactly beautiful -- and in fact rather spooky......

But you can see the prominent crag about 35 feet above where the big stone finally came to rest.  I have always thought that this crag is the source of the big stone -- so I climbed up and fought my way through gorse bushes to have a look at it.  This confirmed my belief, and I was interested to find five other big stones up there, in quite precarious positions, ready to crash down, when the time is right, in the general direction of the black plastic monstrosity. 

So the crag is now in an advanced state of decay, and it seems entirely reasonable to conclude that during the thousands of years of periglacial climate at the end of the Devensian glacial episode, frost action did the job of loosening these blocks.  Other loosened blocks actually fell down the rock face.  Now, with the advent of a full interglacial climate, biological processes have taken over, and it may be that the roots of gorse bushes and small trees will widen cracks and contribute to the next set of rockfalls.  Maybe archaeologists and JCBs will accelerate the process.......