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Wednesday 20 August 2014

Are the pink granite erratics from Lundy?

The Devil's Slide on Lundy Island -- pink granite galore........

So could the pink granite erratics at Flat Holm and Saunton have come from Lundy?  The answer is "yes" --  nothing is impossible unless the laws of physics (known and unknown) are broken.  For the ice of the Irish Sea Glacier to have picked up Lundy Granite and taken it 80 km or more to Flat Holm it must have flowed west towards east with a slightly northwards component as well.  For it to have reached Saunton, that would have been pretty straightforward -- the coast is only about 25 kms to the east of the island.  

But we must also beware of simplistic interpretations here -- the erratics might have followed zig-zag courses, and they might have been picked up and dumped several times by glaciers, sea ice or other processes before ending up where we see them today.

3 comments:

Myris of Alexandria said...

A strong possibility and were it so a very interesting fact.
M
There was quarrying on Lundy for the granite, if the Flatholme granite is from Lundy can we be sure that it is not Victorian ballast. Or even little proto-Welshmen in dugouts.

BRIAN JOHN said...

We can never be 100% sure about ballast -- but as far as I am aware ballast was always capable of being manhandled. If the boulder is too big to lift and heave onto a cart or a sailing ship, it's probably not ballast. Something the size of a human skull is best for ballast -- easiest to load.

AG said...

Having owned a 60ft scottish 1930's Wooden Fishing Boat.

I can confirm that the ballast consisted of 1/2 shoe box sized squared off lumps of granite; sized to fit between the hulls timber framework.

As Brian surmised, they were of a size to allow the average strength crewman to quickly unload them from the hold.

On a timber vessel, Much heavier odd shaped lumps would not only have been awkward to secured;it does have to be secured! but
would also have posed a danger to the vessel's hull planking.