The Chalk Escarpment

 Above -- the chalk scarp at Beacon Hill, near Devizes.  Below: the chalk scarp near the Westbury White Horse.

I'm increasingly convinced that the chalk scarp holds the key to the origins and the transport of the bluestones.  The edge of the chalk downlands of Wiltshire is generally marked by a very steep scarp which is seldom straight, but broken up into a multitude of rounded spurs separated by indentations in the form of steep sided dry valleys or coombes.  There are a few gaps in the escarpment where larger rivers have cut back into the downland,  but the map on the last post shows how prominent this chalkland edge really is.

It is and was a formidable barrier -- it may have been a barrier to the ingress of glacier ice from the west during the Greatest British Glaciation (c 450,000 years ago?) and it must also have been a major barrier which effectively set a western limit on the stone collecting expeditions of the Stonehenge builders.  Did the ice edge coincide with the escarpment?  Further research is needed on this.