Anglesey, The Menaian Platform

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The Menaian Platform and Mynedd Bodafon from Mynydd-mwyn-mawr, Llanerchymedd, Ynys Mon © C. Duigan.

18 July 2014.

Geological terms are often descriptive and precise.  The geologist Edward Greenly described Anglesey as a “platform” – “an old base level of erosion standing now at a height of some 200 to 300 feet above the sea”.  Immediately you see a land surface ground down, flatten by ice and surrounded by water.  Greenly estimated that the total area of the plateau, “which may be called The Menaian Platform, cannot be much less than 400 square miles.”

It was a beautiful sunny morning.  It would be a hot day as the overnight rain seemed to be still evaporating creating steamy views across the island.  Outside Llanerchymedd the delivery driver was feeling the heat as he became impatient while I backed out of his way into a farm yard so he could resume his deliveries.  But I was almost at my destination.  I need not have worried that the hedge would be too high to find the view of The Menaian Platform which was included in Greenly’s Geology of Anglesey (Plate L, facing page 780).  I stopped at a field gate and low stone wall just beyond Mynydd-mwyn-mawr Farm.  Greenly had picked a good spot in the heart of the island.

The blue sky met the green fields of Anglesey along an almost straight skyline.  In the distance Mynydd Bodafon was the only protrusion above the horizon.  As Greenly described all the small hills and depressions in the intervening view seemed to melt into the platform surface.  Even the Menai Strait can be considered a hidden trench in this landform which extends beyond Anglesey to the foothills of Snowdonia.  Although the land appears horizontal at this spot, it actually dips gently to the west, with an average inclination of 6.9 feet per mile.  It is also thought to have extended beyond the current area of the island but this larger landmass has been lost to erosion over time.

I wonder why Greenly did not call this geological landscape The Anglesey Platform?

Anglesey has an internationally important geological heritage.  If you want to learn more check out the GeoMôn website.
http://geomon.co.uk/

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