The Ross-on-Wye one is interesting, as it's still possible to detect much of the scar left by the old meander.
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| From a talk by Moira Jenkins, "The Geology of the Wye Gorge" geology.malvernu3a.org.uk/talks/2012/Wye%20gorge/index.htm |
The walk started with a pleasant climb through Forge Wood, once an important source of wood for charcoal production, needed for smelting iron ore. There were signs of recent activity by Forest England...
... which became rather more obvious at the top of the hill, where their vehicles had turned the track into a mud bath. Oh the joys of rambling in the rainy season!
Leaving the mud behind, I was greeted with this colourful sight. After Storm Ciara we had to replace a couple of fence panels, but they're very dull in comparison with these.
Soon the distinctive V-shaped valley of the Newland Meander came into view. It's time for a bit more geology – a subject that fascinates me. If it bores you, skip down to the photo of me, sitting on a bridge parapet.
The present course of the mighty River Wye is on the left of this map, whilst Valley Brook flows on the course of the old meander. It all looks clear enough, even though Valley Brook is some 90 metres above the Wye, but there's a problem...
Zooming out, you can hopefully see that the meander scar can only be traced to a point near Newland. It's logical to presume that it should rejoin the Wye somewhere near the top of the map, but where? There's a lot of high ground in the way.
I'm little more that a fumbling amateur when it comes to geology, but if I'm interpreting a collection of scholarly articles correctly, it would seem that the Newland Meander is much older than the Ross and Bigsweir ones. Millions of years ago, long before the last ice age, the plateau on which the Forest of Dean stands was much higher, but over time the upper layers were eroded away, taking with them traces of Newland Meander north of Newland itself. Only the deep incision, where the ancient water flow cut through the carboniferous limestone remain. If I've got that wrong then maybe some more learned soul* will enlighten us.
* A learned soul has indeed commented. Take a look at the second comment to this post by someone who clearly knows their subject.
End of attempted geology lesson. Here's the promised photo of little me near Lodges Farm, where the track crosses Valley Brook.
Below Lodges Farm the V-shaped valley continues past a series of ponds. A couple of local residents posed for a photo.
Finally, here's a lovely view of the River Wye, photographed as I approached Redbrook. The old railway bridge has featured on this blog before (here), when I went hunting for millstones.
Still very damp, I see. But better weather has come to Sussex, and to you also I hope. Love the pencils!
ReplyDeleteLucy
Hi Angie, thanks very much for your blog and photos. The ancient meanders of lower Wye are fascinating. I think the idea is that this part of England and Wales was submerged beneath a shallow sea in the Cretaceous period when layers of chalks and clays were deposited on top of much older surface of folded rocks of sandstone and limestone. Around 65 million years ago the land began to rise (or the sea level fell) and meandering rivers developed on a flattish land surface draining into sea to the south. Over millions of years all the soft chalks and clays were eroded and the meandering River Wye eventually began to cut into the hard rocks below. The meandering course of the river was superimposed on the complex geology below. Then over the last 2 millions years, during several episodes of the glaciation, the Wye cut down over 200m through the limestones and sandstones to the current sea level. As it did so some the meanders were eroded through at their narrowest points, leaving an abandoned loop of river channel high and dry, as at Newland. This happened at different times so some of abandoned meanders are higher above the current river than others. One of the most recent meander cut-offs is in Monmouth and the former channel of Wye is still liable to flooding. This has been referred to as the 'Lost Lake' of Monmouth. The next cut off to come is probably in Tintern where there is only a small neck of land in the meander loop opposite the abbey - but we may have to wait until the next glaciation until the river has enough energy!
ReplyDeleteThank you very much for your fascinating answer. If I understand you correctly, then, the Newland meander was indeed 'lost' much earlier than the Bigswear one. I'm still a bit confused as to why the scar from the southern part of the Newland meander has survived so well, whereas the northern section has disappeared, but I'm guessing that the southern bit was gouged out to its present shape by ice age melt water.
ReplyDeleteAngie
Hi Angie,
ReplyDeleteYes, Newland must have been much earlier than Bigsweir. The current form of the Newland loop is as you say probably greatly influenced by the streams that have subsequently occupied the northern and southern parts, especially during glacial and peri-glacial episodes. Probably also relates to the geology with harder limestones and conglomerates in the northern part which may have been more resistant to downcutting.
ANdy
Thanks again Andy. I find all this enthralling and wish that I knew more about the subject. Several years ago, shortly after I moved here from Cornwall (another geologically fascinating area), I thought about joining a geology night school in Ross. In the event, I chose to learn the ukulele... and the rest (as they say) is history.
ReplyDeleteAngie