Phreatic Action!!

[Paz Vale]

Thanks Pitlamp.

I'd already done a trawl on you tube for clips and there are those which show sediment transport, though nothing which showed process in any detail.

I've seen the features you describe in a number of phreatic caves, most notably in some of the  resurgences around the Cuetzalan area which are completely flooded for most of the year.  In some cases the vadose like canyons and vertical rills are cut in (and through) the chert bands which are abundant in this area, suggesting physical erosion.

The paper by Graham & Charlie along with, amongst others, Newsons 1971 paper in Trans. of the IBG. highlight the importance of abrasion in cave formation although as you say some cave scientists and most non-caving geomorphologists don't fully appreciate its importance. 

I'm currently conducting research into aspects of speleogenesis in the limestones of the Staffordshire Gulf, which in many places, given the high silica and haematite content, are resistant to solution and physical processes may play the dominant role very early on in the formation of some of the caves. The question about film footage was basically aimed at getting my supervisor, a non-caver whose knowledge of karst is limited, to appreciate the effects of abrasion in phreatic development.

 

[MadPierre]

Sleets Gill Cave, the main gallery is well worth a look. Very impressive. The grovel through 'hyperthermia' was a bit grim though.

 

[MadPierre]

Sleets Gill Cave, the main gallery is well worth a look. Very impressive. The grovel through 'hyperthermia' was a bit grim though.

Sleets Gill, is in the Dales of course, not Derbyshire; still worth a look if you get the chance. Make sure the weathers been dry for a bit, its a flooder.

 

[Les W]

Sleets Gill Cave, the main gallery is well worth a look. Very impressive. The grovel through 'hyperthermia' was a bit grim though.

Sleets Gill, is in the Dales of course, not Derbyshire; still worth a look if you get the chance. Make sure the weathers been dry for a bit, its a flooder.

More than this. Sleets Gill floods unpredictably and even if it has been dry in the area for some time. I believe it responds to rainfall falling in another area, after around 24 hours. I could be wrong on the numbers but it is in that sort of timescale. Take care.

'tis very fine though. 

 

[kay]

More than this. Sleets Gill floods unpredictably and even if it has been dry in the area for some time. I believe it responds to rainfall falling in another area, after around 24 hours. I could be wrong on the numbers but it is in that sort of timescale. Take care.

'tis very fine though. 

I thought it was even longer than that - I thought I'd heard up to 4 days.

It floods from below., which is why there's a delay.

What I was told was that if water is flowing from the Wharfedale Sump into the main passage  at the bottom of the entrance slope, you shouldn't go in. (That is not to say that if there isn't water there that it's OK).

 

[Pitlamp]

Sorry folks - been away on a caving project.

Paz - your comment about erosional features cutting through non carbonate rock is interesting; I'd not thought of looking for that whilst swimming about in sumps in the north of England but I will do in future.

Duncan's point about large cobbles moving around when suspended in an uphill current is a good one; in the downstream sump of Hurtle Pot there's a large area (i.e. the floor of a chamber) of "dinosaur eggs" - some over half a metre long. These are at the base of a wall up which a powerful current blasts in wet conditions. They are usually in a different position after each flood event. With those monsters hammering into the walls it's not difficult to imagine the contribution which physical erosion makes.

Graham - I'll try and have a look at that paper; thanks for the suggestion.

Folks - don't mess with Sleets Gill if there is any doubt . . . .

 

[Mrs Trellis]

Surely speleogenesis commences as soon as the limestone becomes part of the phreatic zone ?

For example - did the Winnats downcutting expose Suicide or was the Winnats formed as now before Suicide was formed?

Nice little poser for you John - how old is the water you swim through - or any other water for that matter?

 

[Pitlamp]

Interesting one about Winnats / Suicide. I don't know the answer but I'd have thought that the Winnats has been forming for a very long time (since the Carboniferous according to TDF as a submarine trench). The Winnats is still forming today. So my guess is that the proto-Winnats formed well before Suicide Cave. Suicide Cave is much more recent - but got truncated during later stages of development of the Winnats. (Is its original destination some of the old phreatic stuff in the Halfway House extensions in Speedwell?)

 

[graham]

I am not particularly familiar with Winnats / Suicide, but I'd be surprised if the cave, at least in part didn't long pre-date the valley. Two comments

Mrs T. Deej Lowe will tell you that speleogenesis starts about half an hour after diagenesis is complete. I exaggerate, but not by much. I also disagree, except to say that, yes, speleogenesis will start as soon as water circulation is possible within the limestone and this will clearly pre-date the current land surface, especially in areas subject to Pleistocene glaciation.

Pitlamp, you say that the Winnats is still forming today. Is it? Certainly it will be being modified by sub aerial erosion of the valley sides but I would doubt whether downcutting is actually taking place at present.

 

[Mrs Trellis]

Surely solutional activity commences immediately the limestone is in the phreas whilst corrasional activity begins when free circulation of water commences?

My guess would be that large entirely phreatic in origin tubes like those mentioned in DYO, Peak, WICC are very old in origin.

Does anyone believe there is phreatic development of these tubes during glaciation? Is there evidence of underground ice flow? If so that would be a terrific corrasional force.

 

[Pitlamp]

That ribbon of modern tarmac down the centre is a bit of a problem for erosion! However any landform above sea level is subject to ongoing erosion so the valley is likely still to be developing (albeit slowly). However the point I'm trying to make is that the Winnats has a long and complex history and any "before or after" question (re Suicide Cave) is likely to be an oversimplification. I'm not an expert on this particular part of the Castleton area so maybe I'd better shut up and go caving.

 

[graham]

Oh dear why do I open my big mouth sometimes ....

Solutional activity by itself cannot really do very much until there circulation of water, otherwise where does the dissolved material go? Once circulation is under way, it's not long at all before the voids become large enough for turbulent flow& then stuff really takes off.

All sub-aerial landforms are, of course, subject to erosion, but in the case of a valley or gorge, if material isn't being removed from the bottom by a surface stream (even an intermittent one) but, rather is aggrading one the valley floor, then the slope sides will be becoming more gently graded with regard to the proximate parts of the valley floor. Add to that the possibility of plateau surface lowering due to solution, as is certainly the case on limestone, and the vally itself will be over time become a less profound feature in the landscape, shallower and with gentler sides, so it cannot really be said to be "developing" with the all implications that term has.

 

[MadPierre]

The peak district information website has the formation of Winnats down as 'a long collapsed limestone cave system',  is this actually the case? Some of the other stuff I've read on Winnats seem to suggest it was formed as a tidal channel through reefs. So presumably the trench or channel formed first? Is the information on the website below wrong?

http://www.peakdistrictinformation.com/visits/winnats.php

Sorry.. if I seem to have wandered off topic.

 

[langcliffe]

The peak district information website has the formation of Winnats down as 'a long collapsed limestone cave system'

This is the traditional view. The current consensus of opinion favours it being a reef channel re-excavated by melt water in the last Ice Age.

 

[Pitlamp]

There can be a substantial stream flowing down Winnats in wet conditions but this is intermittent.

 

[graham]

Is that stream actually downcutting (tarmac aside), or is it growing a debris fan at the outlet of the valley that serves to in effect raise the base level instead?

 

[Pitlamp]

Hard to say which process is "winning".

 

[graham]

Which probably means that, in the short term at least, the valley profile is stable.

 

[Mrs Trellis]

Imho the valley profile has been most recently shaped by glacial flow - the drainage being underground in the interglacials. The current change is by erosion in the cliffs of Shining Cliff on the s. side. They closed the road last year for a week or so to stabilise.

Btw - anyone know what that interesting little hole is opposite side of Suicide up a well trodden path virtually overlooking the Speedwell shop?