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Thursday, 7 June 2018

Ice shed country -- Cambrian Mountains

Llyn Cwm-byr, near Pumlumon

I keep on discovering fascinating landscapes.  I discovered another one the other day, while travelling home from giving a talk in Bishops Castle, in the Welsh Borders.  We took  detour off the Newtown - Aberystwyth road and took minor roads via Devil's Bridge to Pontrhydfendigaid and Tregaron.  I had been that way before without seeing much, but this time it was a real hot summer's day, with blue sky and fantastic visibility.

This is part of Wales's empty quarter, with a rolling -- almost prairie - like -- landscape of broad river valleys, wide depressions with lakes in them, and hilly areas with gentle slopes.   This is the core of the Cambrian Mountains and the main watershed of Wales, with some streams flowing west and others flowing east -- but no glaciated troughs.  During the big glacial episodes this area has been at the heart of the Welsh ice cap -- so there has been very thick ice sitting on this landscape -- but it has done virtually nothing in terms of landscape modification.   The ice has been effectively stagnant, and probably cold-based,  maybe with occasional aerial scouring but no streaming.  The whole landscape reminded me of parts of the basalt plateaux of NW Iceland, except that here there are the remnants of a very old fluvial landscape which has been largely unmodified for millions of years.

Must try to get back there soon, so that I can take a more careful look.......

The Cambrian Mountains of mid-Wales, between Aberystwyth and Newtown.  The undulating "watershed plateau" is clearly seen in the centre of the map.  The brown-coloured area is the highest part of the plateau, around Pumlumon.

Typical landscape on the plateau

Extract from the BGS glacial map of Wales, showing Devensian ice movements at the centre of the Welsh Ice Cap.  Note the outlet glaciers flowing away from the ice-shed area -- the Rheidol and Ystwyth Glaciers flowing west, and the Wye and Severn Glaciers flowing NE and SE respectively.  


Herbert M Sauro said...

I used to live in Pontrhyygroes, one of my favourite places of all time. You're right that there are great swathes of open boggy grass on the top. I called it the Cambrian Plateau when I lived there. It must be over 1000 square miles of nothingness behind Pontrhyygroes. No one lives up there. I hiked up there quite a bit. When I lived in the area there was the story of the Beast of Bont that lived up in the moors, killed quite a few sheep. As for the trees, there are a few deciduous trees on the plateau so it shows that trees can grow there and presumably, as you suggest it was forested at one time.

BRIAN JOHN said...

I was greatly taken with a wonderful book called "Good Men and True" -- about the special breed of tough pioneers (or stubborn old folk who just hung in there) who lived up on the plateau. What a hard life they had to endure......

And one of my favourite roads in the UK is the Abergwesyn Mountain Road, a bit further south. Everybody should drive along it before they die.....especially when the skylarks are singing.

TonyH said...

Plynlimon and other parts of the upper Wye valley features in the first of a series of BBC documentaries on The Wye. This starts tonight on one of the BBC channels, and was first shown on BBC Wales apparently.

As an ex - librarian, I habitually trawl through the internet. I did this around 6 months ago for a Post Brian had done about, I think, the Red Lady of Paviland (or something similar) and discovered that an Oxford "boffin" is/was claimimg that there used to be twin men in the Tregaron area whom the locals (and others) seriously claimed had Neanderthal appearances. Remember?

I used to drive by motorbike regularly across the terrain from Builth Wells via Rhyader to Aberystwyth, and have also done a trip from the latter to Tregaron and Lampeter. Wonderful, liberating journeys.

Herbert M Sauro said...

Totally agree with you about skylarks and the mountain road. I used to hear skylarks a lot as a kid. The mountain road was the quickest way to England from Pontrhyygroes, I used the road to get to the second-hand bookshops in Hay-on-Wye.

RackRunner said...

Looks like a nasty place to get lost ! I wonder how people found their way around?

Penrodyn said...

"twin men in the Tregaron area whom the locals (and others) seriously claimed had Neanderthal appearances. Remember?"

I know that story! In fact, I heard that the local school would take school kids, as part of their history lesson, to visit the family where they would all have tea and cake.

Penrodyn said...

"Looks like a nasty place to get lost ! I wonder how people found their way around?"

One of the main issues is that there are some boggy areas where you can sink into and I found a number of sheep who had succumbed. Not a nice place for sheep in general as the farmers would only rarely venture up to check on the flock.

Of interest is is also a lesser known Roman marching camp on the plateau northwest of Rhyader.