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Tuesday, 20 January 2015

A Sleek Stone super-erratic?

The more I think about this, the more convinced I become that there was a single "super-erratic" in approximately the position now occupied by erratics 1 and 2 on my little list.    One reason for this is the fact that Cantrill and colleagues (in 1916) only referred to ONE erratic here, whereas today there are obviously two, made of the same material.  The second reason is the appearance of the erratics  -- blocky, rather angular and showing few of the "sub-rounded" forms often associated with glacially transported blocks. Look at these photos:

The rucksack rests on a relatively clean fracture face with a very sharp edge.  The smaller boulder is on the left.  Beware -- the smaller boulder to the right of the rucksack is not igneous.  It is a boulder of flaggy sandstone which has come from the cliffs nearby.

One of the more rounded (and ancient?) faces of the large erratic.  Notice that there has been a loss of a large chunk of rock from the top surface.

 The smaller erratic boulder -- remarkable for the sharpness of its edges.  Note that the left face appears less weathered than the others.

End-on view of the large erratic (and the local sandstone boulder to its left).  But note the large fracture running across the igneous "super-erratic" -- maybe it will disintegrate further, before too long........

Erratics 1 and 2 sitting on the bedrock platform.  Forget about the local boulders in the foreground.  It looks as if there are 3 erratics here on the rock platform -- but the apparent smaller one covered in barnacles, closest to the camera, is in fact still joined to erratic 1.  For how much longer?

I'm going to stick my neck out here and suggest that in 1916 there was a super-erratic weighing between 95 and 100 tonnes here, and that it has subsequently been broken up into at least two pieces.  Was the damage done during the tremendous storms of January 2014?  We know that much of this coastline was transformed at that time -- with about 2m of sand stripped away from local beaches, leading to exposures of the submerged forest.  I think the monster erratic broke up earlier than that -- since there are no REALLY fresh fracture faces visible at the moment.  I'd like to go back -- I think there may be some more chunks from this super-erratic waiting to be discovered.....

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