Roches moutonnees on the north face of Mynydd Preseli

 

The roches moutonnee forms on the north face of Preseli -- photo courtesy Preseli 360

I have written often in the past about the roches moutonnee features on the north face of Preseli, but I have never before seen a photo that captures the forms so well.  Here we can see Frenni Fawr, Foel Drygarn, Carn Breseb and Carn Goedog and their distinctly asymmetric forms -- gentle north-facing up-glacier slopes and steeper plucked faces on their south-facing or down-glacier sides.  When ice has moved across this landscape from left (north) to right (south) abrasion has been concentrated on the northern flanks and plucking or quarrying concentrated on the southern flanks. "Quarrying", by the way, is a specialist term often used in glacial geomorphology, with no suggestion at all of human involvement in the process.

As I have often said before, the extraction of blocks was much more likely on this side of the Preseli ridge than it would have been on the southern flanks.  It's all to do with the laws of physics........