The ice that carved our county
Last updated 05:33, Friday, 06 June 2008
Geologists have a different perspective on life to us mere mortals. Alan Smith says our climate is getting colder. That is in the short term. His short term. And his short term is ten thousand years.
The Ice Age in the Lake District by Alan Smith. Rigg Side. £3.99
That is the date of the last great ice age that swept across Cumbria and scooped and moulded, cracked and crumbled, excavated and extruded and shaped the fells and lakes and valleys we know today.
His argument is based on the Milankovitch cycles which explains how after 10,000 years or so we can expect a glacial period of 90,000 years and it looks like our warm spell is almost up.
Looking back 18,000 years, the Devensian Ice age was at its worst. A vast and intolerable weight of glacial ice spread across Northern Europe and all of Britain except, of course, the favoured, pampered south.
Cumbria crumbled under its very own ice-cap and glaciers flowed down the valleys creating the familiar spokes of the wheel.
These glaciers collided, in their immensely slow, inevitable way, with the glaciers sloping off from the Scottish Uplands and together they cut the Solway Firth and flowed into the Irish Sea.
Erratic rocks were broken off and carried for miles and then dumped as the ice melted.
These rocks, found dotted over the country far from their place of origin, reveal how the ice flowed. Rocks from Criffel in Dumfries are found all across the Solway Plain and down the west coast as far as Furness. There’s a huge rock of Criffel granite on Allonby beach.
We exported Shap granite along the Stainmore Gap and into Yorkshire long before Shap Quarries began their excavating.
When things were at their coldest, the dome of ice that covered the mountains could well have been over 1,800 metres thick, rising 600 metres above the peaks.
Things would have been very, very cold. Average temperatures on the surface would have been minus 18 degrees and the ice beneath would have been frozen solid to the ground.
As the temperature eased so the iced began to flow, more readily to the south and west, and it is this movement that has left its deep mark on the landscape we know.
The movement of the ice and the geologist’s imagination have produced a whole menagerie of land forms.
Whalebacks are the elongated ridges running along the line of the valley and the line of ice flow. They can be seen near Puddingstone Bank in the Watendlath Valley.
When the ice is thinner and more fleet of foot, the pressure is less and roches moutonees are formed. Geologists thought these rocks with one steep and one gently sloping side looked like sheep lying down. Look at the rock at Yewdale near Coniston. A tail of glacial till is to be seen behind the resistant crag of Castle Rock south of Keswick.
The high fells to the west and south were scoured by the ice, but, perhaps surprisingly, the round smooth domes of Helvellyn, and the other northern fells show little sign of being troubled by the ice. Helvellyn’s summit is so flat that some madcap pilots landed a plane on it in 1926.
And then there was the ice cutting and shaping, creating the cirques and tarns and ridges and hanging valleys and moulding the very fabric of the landscape.
That fine poet and topographer from Millom, Norman Nicholson, understood a thing or two about his native county: “It has been said that when God made England his finger touched but did not press, but that is not true of Cumberland and Westmorland. He pressed there all right. What is more he used his nails. And his nails were ice.”
Alan Smith’s splendid guide to the ice age in the Lake District is detailed and technical but presented with an enthusiasm that makes everything crystal clear. It should be in every thinking walker’s rucksack.
The Ice Age in the Lake District is available from Bookends, 56 Castle Street, Carlisle, and 66 Main Street, Keswick and from www.bookscumbria.com
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