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Sunday, 22 June 2014

The great overhang at Sron Uladal, North Harris

While we are on about the Outer Hebrides, it's worth making mention of the one of the grestest natural wonders in the UK, namely the great overhanging cliff at Sron Uladal (note:  many different spellings) on the Isle of North Harris.  Below I reproduce a series of photos of the overhang, made famous by a filmed climb by some maniacs who climbed up it -- while presumably avoiding the actual overhanging bit.........


The great cliff is seen at the centre of this map, just to the south of the lake.  It can only be reached by a long walk from the B877 road to Hushinish.  When you get there this is what you see:

 The above images are from the west side of the spur end

This image is from the east side of the spur end

This one looks at the spur head-on (from the north)

This one was taken from high on the valley side, across the trough which runs northwards on the west side of the precipice

This is in some ways the most extraordinary image of all, from Google Earth.  It effectively gives us a 3D impression of the end of the spur, seen from the north across the waters of Loch Uladal.....

So why was this overhanging, undercut feature created?  There must be extraordinary coherence in the rock on and above the overhang -- although of course it will one day come crashing down.  The overhanging section is about 50m high.  One would normally expect overhanging sections like this to be created on the outside of bends in deep glacial troughs, where erosive forces are concentrated.  But here  the undercutting has been done at the confluence of two very active glaciers coming together at the position of a truncated spur.  The western valley in which the footpath lies is a spectacular one,  but the eastern valley is not at all so spectacular -- and one might speculate that it carried a powerful glacier which had its origins in the high mountains of North Harris further to the east.

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