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Saturday, 21 August 2010

Glaciation of the Mendips

Somebody mentioned to me the other day that the thesis of glacial activity affecting the Mendips is coming back into fashion. I'm not sure what the new evidence may be, but am reminded that Geoff Kellaway and a few others have been convinced for many years that the deep gorges in the Mendips are not simply the result of karst processes including elongated cave collapse. If there really are glacial deposits in the vicinity of Bath, and not far from Glastonbury, then it is almost inevitable that glacier ice either pressed onto the flanks of the Mendips or overrode the hills entirely. Just found this extract:

From Geotimes May 2005
by Megan Sever

Ice sheets reached as far south as Cheddar, but the bigger factor in shaping the landscape was actually the meltwater once the glaciers receded during interglacial periods. After each ice age, glaciers released a torrent of meltwater through the Somerset rivers to the sea. Carrying boulders and gravel, the rivers scoured out gorges like Cheddar Gorge up to 400 feet deep and 3 miles long. Throughout time, as sea level has risen and fallen, Cheddar Gorge has gotten deeper and shallower. Along the climb to the ridge of the gorge, you can see various layers of limestone.

The Mendip Hills in Somerset, seen here on the drive to Cheddar Gorge, have been extensively shaped by glacial processes starting 1 million years ago. Today, sheep farms grace the rolling hillsides.

While the surface landscape was being carved by glacial meltwaters, underground rivers were similarly carving out vast caverns, such as Gough's Cave and Cox's Cave, the two caves in Cheddar Gorge. Floodwaters and underground rivers dissolved the limestone, slowly sinking lower and lower until they hit the harder sandstone layer and leaving caves above.

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