Wednesday, 13 April 2016

Rocks, rivers and the shaping of the Clyde and Avon Valleys...by Katie Whitbread

Corra Linn, a 27m high waterfall in Devonian
sandstone in the gorge of the Falls of Clyde. 
The Clyde and Avon Valleys lie just a few kilometres outside Glasgow. Their fertile slopes have long supported orchards and fruit farms, their stone once built palaces, and their coal and ironstone fed the industry of Scotland’s largest city.

Last Autumn, I was commissioned by the Heritage Lottery Fund supported Clyde and Avon Valley Landscape Partnership to assess potential sites for a geological trail. I laced up my boots, grabbed my camera, and took to the field, rooting out the grand, the powerful, and the downright puzzling from the wealth of geological features in this rich landscape.

From the high point of Blackhill, a ridge of resistant igneous rock fortified during the Iron Age, to the depths of the River Nethan Gorge, etched deep into Carboniferous sedimentary rocks, where miners once burrowed for coal, the Clyde and Avon Valleys highlights the intimate links between people and the geological past.

Perhaps the most powerful of the many geological stories that unfolded as I explored, was the testimony of these valleys to the power of rivers to shape our land. Devonian sandstones bear witness to ancient braided streams, whilst the coal-bearing Carboniferous rocks are the remains of meandering rivers that once snaked through vast swampy flood plains.

But, it has been the interaction of glaciers and rivers in the more recent geological past that has really left its mark on the land. This region of Scotland was blanketed by glaciers some twenty thousand years ago and as the glaciers retreated, water and sediment ponded up in front of the ice margins. Catastrophic drainage of these lakes, and the powerful flows of young postglacial streams, excavated dramatic gorges up to 80 m deep that form characteristic features of the Clyde and Avon Valleys.

Sampson's Slingstane, a 4m diameter boulder perched
on the rim of the gorge above the Fiddler Burn.
At the Falls of Clyde, the rolling ‘kame and kettle’ topography of ice-marginal sand and gravel masks the buried former valley of the River Clyde, now infilled with glacial sediment; whilst nearby, the modern River Clyde thunders over picturesque waterfalls in a deep gorge excavated into Devonian sandstone during the outburst flood of a large pro-glacial lake. Some of the regions’ more enigmatic features may also owe their existence to the interaction of glaciers and rivers. The dry valley of Auchenglen may once have carried the waters of the now diverted Mouse Water, whilst the precariously perched boulder of Sampson’s Slingstane, tumbled, perhaps, from the margin of a glacier or rolled in a huge flood of meltwater, clings to the gorge rim above the Fiddler Burn.

The gorges of the Clyde and Avon Valleys are havens for ancient woodland, and their scenic landscapes have attracted tourists and inspired poets and artists for generations. It was a privilege to investigate geological sites that once inspired William Wordsworth and Sir Walter Scott. The Shaping Our Landscape Geological Trail will help many more generations to be inspired by the beautiful landscape and rich geological heritage of the Clyde and Avon Valleys.



For more information see the article in Earth Heritage Magazine

Report on the geological sites for the Clyde and Avon Valley Landscape Partnership can be read here

The hunting lodge of Chatelherault is all that now remains of the grand Hamilton Palace. Sandstone from quarries in the
Clyde and Avon Valleys was used in the palace construction. The low ground to the right is the remains of a former sand and
gravel pit into the deposits of a delta that formed in a pro-glacial lake that occupied the Clyde Valley. 
With thanks to Kirsten Robb and Sarah o’Sulliven – Clyde and Avon Valley Landscape Partnership

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