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Thursday, 10 March 2011

On ice directions

 Many thanks to my friend Mike Walker for forwarding a PDF of this excellent and comprehensive chapter on the Quaternary.  It dates from 2006 -- and if we home in on West Wales we will see that almost everybody now agrees on a Devensian ice limit somewhat similar to that shown.  Mine differs only in that it incorporates the ice-contact tills at West Angle and the kame terrace at Mullock Bridge, which both show that the ice pressed into the mouth of Milford Haven.

Now for a little gripe.  Why do quite senior academics continue to show ice movements parallel with ice margins?  That just does not happen, except in the rarest of circumstances, where topography (eg a scarp or a deep glacial trough) forces glacier flow.  The ice did NOT flow across western Pembrokeshire from NE towards SW.  Has anybody recorded striations or erratic transport in that direction?  Not that I know of.  No -- the ice behaved as ice always does, and flowed perpendicular to the ice edge.  That is, it came in from the NW and flowed towards the SE, with minor variations forced by landforms.

Have you got that, chaps?


Reference:
Catt, J.A., Gibbard, P.L., Lowe, J.J., McCarroll, D., Scourse, J.D.,Walker, M.J.C., Wymer, J.
J., 2006. Quaternary, ice sheets and their legacy. In: Brenchley, P.J., Rawson, P.F.
(Eds.), The Geology of England and Wales, second ed. The Geological Society,
London, pp. 429-467.

8 comments:

Constantinos Ragazas said...

Amen to that, Brian! I also had to make the same exact argument on at least one occassion that the ice edge does not indicate the direction of ice flow movement. But rather the flow is perpendicular to the edge! It's a simple idea that my multivariable calculus students had no problem understanding!

Kostas

Robert Langdon said...

Norman Hammond's comments today (10th March 2011) in The Times seems to suggest your theory of ice movement bring bluestones to Stonehenge region is dead? After the 'scientific findings' by Richard Bevis of the National Museum of Wales.

Quote: "The notion that the bluestones were brought from Wales to Wiltshire by glaciers during the Ice Age is now discounted."

On a more positive note (for me) at least they recognise the stones came to Stonehenge by boat - although the route suggested is ridiculous!

Slowly but surely.

RJL

BRIAN JOHN said...

Who is Norman Hammond? Does he know anything at all about bluestones and glaciers? I doubt it -- and I can't be bothered to pay £1 to look at The Times in order to find out.....

Constantinos Ragazas said...

Brian,

Such a vicious campaign of misinformation! I am shocked and dismayed! What do you reckon is the deep underlying reason for it?

Constantinos

BRIAN JOHN said...

Oh, the establishment always was deeply conservative! I imagine Hammond is just trotting out the traditional story -- and does not have the background experience to see what the new geology is really pointing to. Shall we be generous and just say he is probably confused....?

Anonymous said...

Norman Hammond appears to be a specialist in central American (or Mesoamerican) archaeology and is based at a U.S.University, so is clearly well qualified to be not only The Times' Archaeology correspondent, but to be commenting upon all matters regarding British archaeology.Why couldn't The Times find someone who at least is BASED in our country, or is that asking too much at a time when the recession is making many archaeologists under-employed if not unemployed. It appears he has held down this job for many years and has now reached 66/67.Answers on a postcard.

BRIAN JOHN said...

Ah, thanks for that. I will try to hunt him down and ask him directly whence he got the ridiculous idea that the glacial transport idea is "now discounted." Whatever his expertise may be, he obviously does not read much geomorphology....

Anonymous said...

In my youth there was a song in what used to be known in those far-off days as the Hit Parade which went:-

(chorus) Norman, Oooh oooh, Norman,
Ooooh, Norman, Norman, my love.

David Jacobs was recently heard playing it - perhaps HE knows something???