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Upper Flood Swallet and the caves of the Blackmoor valley

M

martinr

Well-known member
To stop pepole hijacking other topics, I thought I would start a new thread here for people to discuss the caves of the Blackmoor area (Upper Flood Swallet, Waterwheel Swallet, Grebe Swallet, Blackmoor Swallet, Blackmoor Shaft etc).

To begin with, here is MCG's survey (1976) of the area:


mcgjournal1976planrq4.jpg



The caves are shown with the names used by MCG at that time:

Bank Subsidence, Altitude 237.5m  =  point upstream of UFS where stream is known to sink

Upper Flood Swallet, Alt 237.6m

Middle Flood Swalet, Alt 234.5m = Waterwheel Swallet

Lower Swallets  = points where water seen to sink since 1968 flood, now lost?

Grebe Swallet, Alt ???m. Has also been known as Lower Flood Swallet but see above

Blackmoor Swallet, Alt ???m = MCG dig in 1950's/1960's. Inspected May 2007, no longer accessible

Shaft, Alt 240.5m = Blackmoor Shaft = Stainsby's Shaft



 
martinr said:
cap 'n chris said:
martinr said:
Grebe MUST connect with UFS, somewhere. But it may be easier(?) to connect from the UFS side?
Click to expand...

Agreed. Hence the thought re waiting for UFS surveyors to determine to what extent there is proximity between UFS/GS - if it ends up with a 30m separation through boulders then there seems no point in spending 2-3 years blasting somewhere which is already achievable by an alternate route.
Click to expand...

Draft survey of UFS as far as Walk the Plank (WTP):




If this is correct then Blackmoor Shaft (BSh)  is heading for UFS at WTP where there is an inlet - the Blackmoor Swallet water perhaps?

Horizontal distance between BSh and UFS at WTP is perhaps 70m, but the boulder choke from Golden Chamber to easySqueze has not been surveyed, only estimated. And if it is over-estimated then the distance is less.

Grebe, although heading in the geneal direction of UFS, doesn't align with an obvious feature in UFS yet.

The cornish miners drove Blackmoor Shaft "to get beneath a cavern" and drain the mine. At first glance this could be taken to mean WTP chamber.
Click to expand...

 
cap 'n chris said:
Captain Harpur reported in 1847 that mining operations were suspended in Stainsby's Shaft at the respectable depth of 108m.

A level/adit at 38 fathoms had intercepted a "cavern" 55 metres south east of the shaft on 1st May 1847, although it was not open void, probably rocks/mud - almost without doubt part of the new UFS extensions.



Plug follows....

BTW, if you don't own copies of UBSS Procs, Vol 18, No.1 (re Waterwheel Swallet), Vol 17, No.1 (re Cornish Miners at Charterhouse-on-Mendip) and Vol 19, No.1 (re Grebe Swallet) I strongly recommend them to you or anyone with an interest in the caves/mines of this fascinating part of Mendip.
Click to expand...

 
Splendid, that saves me having to scan & post up the UBSS Waterwheel & Grebe surveys (both done by Willie Stanton).
 
The stream coming into Upper Velvet bottom (sinks @ Blackmoor Swallet & other holes)

is hardly ever seen these days, even in prolonged rain.
There must be further capture higher up.
 
Joan Goddard has just pointed out the similarities between the pom pom formations in Neverland, Upper Flood and those in Steam Hole in Forest of Dean (FOD). Here's a photo of the FOD pom poms:

Ship-badger said:
Wigpool Iron Mine-Sway Hole to Steam Hole-High Level Route
5th April 2006

Present: Greg, Malc,Dave Tuffley, Tim, Gary, Jan, Dave, George, Nicky, Seb, Sue, George Price, Steve Parry, Steve Jackson, Carl, Michael, John, Glenys, Chris Bowen, Chris Stott, Harvey Lomas, Andy and one other.

.............After a bit of cooing at the pompoms, we made our way out through Steam Hole..........
Click to expand...

and here are the Upper Flood pom poms (photo by Mark Shinwell CUCC):



I would be interested to know if anyone can explain how these pom poms form? As they have also been seen in FOD, do any of the Forest cavers have a theory? I dont know what mineral the UF pom poms are, but I assume they are calcite?

 
Deffo calcite. I think there is an explanation in Carol Hill & Paolo Forti's Bumper Fun Book of Calcite.

40.jpeg
 
graham said:
Deffo calcite. I think there is an explanation in Carol Hill & Paolo Forti's Bumper Fun Book of Calcite.

40.jpeg
Click to expand...

Thanks Graham. We have a copy in the MCG cottage (first edition only) - I will look it up this weekend.
 
Looks like pool fingers (see Cave Minerals of the World, ed.2, p.86-87, Hill & Forti, NSS) but formed with a split level "tide". Also known as subaqueous stalactoids (great name!) - these are essentially stalactite shaped speleothems formed subaqueously in a pool. The UFS ones appear to have a double form in so far as the stem has a distinct tide mark, above which I guess it originally would have grown subaqueously when the "tide" was higher, with a later drop down to form the larger bulbous end part. The really nice macrocrystalline example (the one on the near left hand side) is fabulous (but seems to evidence the loss of the bulb at the bottom - presumably a natural break).
 
In fact you can see a higher "tide" mark near the top of Mike's helmet. My considered guess/idea is that "normal" straws originally grew, after which a pool developed engulfing/submerging the straws, upon the surfaces of which the subaqueous crystal coating formed, with a subsequent tide drop to the obvious horizon (marked by the flat "tops" of the bulbous lower sections) whereupon the remaining part below water level continued to accrue the crystalline coating to form the rounded pom-pom base, a final drop in the level of the pool has exposed them - as they presently remain.
 
cap 'n chris said:
In fact you can see a higher "tide" mark near the top of your helmet, Mike. My guess is that straws originally grew, after which a pool developed engulfing/submerging the straws, upon the surfaces of which the subaqueous crystal coating formed, with a subsequent tide drop to the obvious horizon (marked by the flat "tops" of the bulbous lower sections) whereupon the remaining part below water level continued to accrue the crystalline coating to form the rounded pom-pom base, a final drop in the level of the pool has exposed them - as they presently remain.
Click to expand...

There is a photo by Tim Francis of The Cornet- http://www.mendipcavinggroup.org.uk/documents/web339.pdf scroll to Page2 - showing a thin, normal stal growing down from the ceiling which suddenly goes wild after a few cms, so presumably the water here must have filled the passage to within a cm or two of the roof at some time.

The "subaqueous crystal coating"  would form very slowly? Any thoughts on how long?
 
Very difficult to say, as it depends on the dissolution equilibria of the salts in taht location at that time. I am aware of calcite rafts forming in a period of decades rather than centuries* so, in the right conditions it may be quite quickly.


*'cos they were forming on the surface of passage-width pools and were destroyed by the passage of cavers. In that location the previous visit had been no more than a few decades before, possibly sooner.
 
tony from suffolk said:
What truly remarkable formations! Thanks for sharing this excellent photo with us Martin.
Click to expand...

Cheers. The photos were taken by Mark Shinwell of CUCC who has kindly allowed MCG to use them. I wish I could get to Neverland to see the formations, but the squeeze is probably too tight for me.
 
Les W said:
martinr said:
I wish I could get to Neverland to see the formations, but the squeeze is probably too tight for me.
Click to expand...

Won't know if you don't try though   :-\
Click to expand...

Natch. MartinR's chest has been tested in the UF simulator and has been show to be a no-goer. Anyway, Les, since you are now "officially thin" you can check it out at BCRA :)
 
I went into UFS today and got as far as the rift that drops back into the streamway just after "Golden Chamber". I found the rift very tight, though I think I could have passed it with a bit more effort, or by taking a few clothes off. We didn't go any further as we had already left a mate at a squeeze before "Golden Chamber".

So my question is, is the rift I stopped at the tightest point, or does it get even tighter beyond that. If that is the tightest point, then I shall return with thinner friends; but if it gets even tighter I won't bother.
 
IIRC there is a tighter bit beyond the rift. 23cm is the measured smallest bit but there's some 3-D bouldery squeezes before it.
 
Ship-badger said:
I went into UFS today and got as far as the rift that drops back into the streamway just after "Golden Chamber". I found the rift very tight, though I think I could have passed it with a bit more effort, or by taking a few clothes off. We didn't go any further as we had already left a mate at a squeeze before "Golden Chamber".

So my question is, is the rift I stopped at the tightest point, or does it get even tighter beyond that. If that is the tightest point, then I shall return with thinner friends; but if it gets even tighter I won't bother.
Click to expand...

Ive sent you a PM
 
I think the rift out of Golden Chamber is the most intimidating bit (not mind that it *is* intimidating) because its the only squeeze that is of any length; the tightest bit is about 1 metre long, and all the others are point squeezes. But is is definitely *not* the tightest point. Both "Not Easy Squeeze" and "Easy Squeeze" are tighter. Check out "Not Easy Squeeze" at Hidden Earth :)
 
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