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Thursday, 14 June 2012

Glaciers in Devon and Cornwall


Above: Dartmoor - low sun and winter frost.
Below:  One of my attempts to show the small thin ice caps of SW England and their incorporation within the glacial limit of the Anglian Glaciation.


Thanks to Pete G for bringing this to my attention.

Am I allowed to say "I told you so"?  As faithful followers of this blog will know, I have mentioned on many occasions that the uplands of SW England (including Exmoor, Dartmoor and Bodmin Moor) must have carried small ice caps during the main glacial episodes.  Now some new research has shown that Dartmoor did carry an ice cap of its own, and that the ice was at various times thick enough and active enough to create streamlined forms.  Apart from Stephan Harrison, most geomorphologists have been wary of getting involved in the "small ice caps" debate, and it's good to see some serious work at last on this topic, published in a peer-reviewed journal.

We should not be surprised -- after all, the glacial models from Aberystwyth University have been showing exactly the same thing as Evans and Harrison are now proposing on the basis of fieldwork on the moor.

The implications are very big indeed, since if there were substantial glaciers on  the uplands of SW England it is entirely reasonable to suggest that the Irish Sea Ice Sheet also pressed far inland into Somerset and maybe even into Wiltshire.

I hope that some of the archaeologists will now sit up and take notice.

I will try to get a copy of the paper, and will report further, but for the moment we will have to make do with the report from the Western Morning News.......


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Dartmoor developed its own Ice Age glaciers – researcher

Wednesday, June 13, 2012
Western Morning News

http://www.thisisdevon.co.uk/Dartmoor-developed-Ice-Age-glaciers-ndash/story-16355689-detail/story.html

In terms of human history the last Ice Age was the biggest thing ever to happen to the West country – but the question always has been just how far south the vast glaciers extending from the Arctic reached.

It's known that mankind lived in the South West before the Ice Age occurred, but for decades geologists believed the massive ice-wall stopped more-or-less along the shores of the Bristol Channel.

Now, however, new research has discovered there were glaciers far to the south.

By using hi-tech new methods of observation, scientists from both Exeter and Durham universities have been able to establish that huge ice-sheets covered the heights of Dartmoor.

They were so big and powerful that the moving ice-sheets were even capable of lopping off some of the mighty granite tors which would, otherwise, still be a feature of the more central parts of the plateau.

The research, which was undertaken by the two universities and Stockton Riverside College, has just been published in the journal Quaternary Science Reviews.

Researchers, who carried out detailed observations on the ground and using aerial photography, say the evidence includes glacial features such as elongated rounded mounds or drumlins and hummocky landforms or moraines.

They believe similar features may also exist on Exmoor and Bodmin Moors, indicating that upland glaciers would have been a feature of the Westcountry's frozen Ice Age landscapes.

The findings are important as they say a good deal about how some of our most high profile landscapes were formed. Researchers believe the glacier ice helped give the highland plateau its distinctive appearance.

On the highest hills the ice cap – which would have been up to 100 metres thick in places – either destroyed and carried away tors, or prevented their formation over thousands of years.

However, the really big tors found around the edges of Dartmoor – such as Yes Tor, Hound Tor and Hay Tor – survived because they were either left untouched by the ice or because the ice layer on them was not substantial enough to destroy and move them.

Dr Stephan Harrison, of Exeter University, told the Western Morning News: "We are saying the broad high plateau areas in the middle of North Dartmoor were able to produce glaciers and these thickened and then flowed downhill into the valleys. The highest ground (such as the area around Yes Tor) was quite narrow and glaciers on these locations could not develop as successfully."

Dr Harrison is adamant the glaciers would have existed on the moors: "Dartmoor was high enough and big enough to develop its own ice cap," he said.

"The evidence is compelling when you look closely at the landscape – and our research techniques may help us to see if other southern upland areas of the UK were also glaciated and shaped by ice."

Professor David Evans, of Durham University, added: "The story is more complicated than we have traditionally believed.

"A landscape that has been regarded as a classic example of cold, non-glacial processes was in fact covered by a glacial ice cap.

"Dartmoor was the location of the southernmost independent ice cap in the British Isles, the evidence for which is so subtle that researchers had missed it for almost 100 years."

5 comments:

Stephan Harrison said...

Hi Brian
Thanks for this. If you don't have access to QSR I'd be very happy to send you a pdf of the paper. Email me and I'll send it.

Best wishes,
Stephan

Tony Hinchliffe said...

This is indeed significant news, Brian. Nice to see that Durham University is involved in the research, too. And what do you know about Stockton Riverside College? A new one (like this Devonshire glaciation) to me. Well spotted, Pete!

My parents moved to Devonshire simultaneous with my own move to Durham, so I roamed the Devon hills (more towards Exmoor than Dartmoor) during vacations. Ground-breaking news!!

Anonymous said...

Brian,

How does the ice cap at Dartmoor advance your glacier transport theory of bluestones from Preseli to Salisbury Plain? Wrong direction! But glaciers to the southwest of Salisbury Plain along with an encroaching Irish Sea Glacier to the west and north forming glacier dams does seem to indicate Salisbury Plain may have been a glacier meltwater lake at one time. And if so, it could have solidly frozen during the Younger Dryas lasting some 1300 years around 8500 BC. Thus forming a 'local ice sheet cover' over Salisbury Plain. Still in denial over this plausibility?

thinker

BRIAN JOHN said...

Mr Thinker -- yes, I'm still in denial about Younger Dryas meltwater lakes on Salisbury plain. But I won't say more until I have read the paper and digested its contents.....

Anonymous said...

Brian,

Glacier Lake Salisbury would have been frozen solid during the Younger Dryas!

thinker