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Sunday, 19 February 2012

The Fluvioglacial Landscape near Monington

Thanks to Jonathan Lee and Aberystwyth university, here is another stunning image from North pembrokeshire, made by processing digital stereo aerial photography  -- as mentioned before, we can see altitudinal changes to an accuracy of 2m, with the 3D effect caused through the application of "false lighting and false colour." Low level lighting is thrown from the NE.

What we see here is the extraordinary fluvio-glacial landscape in the area around Monington, on a broad plateau surface midway between Newport and Cardigan.  These features have been known for many years, and have been mapped by many fieldworkers including Prof David Bowen and yours truly  -- but nothing before has shown up these features with this level of accuracy.  Notice that most of the landscape is smooth -- but from the centre of the image up to the top edge, and in some areas to the left, the land surface has "excrescences" or rough blotchy areas which look very different.  These are the fluvioglacial accumulations left behind at the end of the Devensian glaciation -- including eskers, kames, kame terraces and even kettle holes where detached ice masses have melted out.  It was the presence of these features that led Charlesworth in 1929 to define the "South Wales End Moraine" in this area -- thereby triggering off endless debate about ice limits and dating.

These features are not particularly "linear" -- so what are they doing here?  Our best guess at the moment is that the ice extended well to the south of this point, and then when melting started, the ice thinned until the hilltops in this area started to protrude -- setting off enhanced rates of melting, and the accumulation of fluvioglacial materials in the pits and hollows thus created.

6 comments:

Robert John Langdon said...

Excellent picture Brian!

Its amazing how clear you see the post ice age watery landscape - I'll use the same technology to illustrate my new book.

Thank you
RJL

BRIAN JOHN said...

It's a free world, Robert. And no doubt you'll have a field day with Glacial Lake Teifi......

Robert John Langdon said...

Brian

Lets not forget 'the big one' lake Harrison - the geological dating evidence on that is only down to archaeological finds - and we know how 'unreliable' it is to use that method of dating.

RJL

Tony Hinchliffe said...

This wonderful image of the fluvio-glacial landscape in that part of North Pembs. has whetted my appetite to go and take a look next time I'm over there in Dyfed generally.

Your mentions of kames and eskers etc etc takes me back to Geography student and personal holiday field trips way back when, particularly in Scotland.

Anonymous said...

Amazing picture!

Can we get one showing the fluvioglacial landscape of Salisbury Plain?

Amazing Grace

Tony H said...

My grand-daughter is called amazing
Grace: Ella amazing Grace. She is 4months old.But who is hiding behind THIS pseudonym? And do I detect an element of sarcasm? Oh ye of little faith, prepare to be confounded........