Phreatic Action!!

Black Ole Bob

New member
Does anyone know how long it takes Phreatic Action to create the larger tubes like those found in Water Icicle Close Cavern, North west passage etc??

And when were they created??
 

Pitlamp

Well-known member
It's not an easy question to answer unfortunately. The reason is the rate of dissolution of the limestone (and also physical erosion in many cases) is affected by so many variables which themselves also change through time. You can't work out age from size.

There are ways to get an IDEA of their ages based on dating stalagmites - but these studies only give an insight into when these phreatic tubes were drained (i.e. once stals can start to grow) not their total age. I'm pretty sure some stal dating has been done in Water Icicle Close - perhaps someone else can point you at where to find this information?
 

Black Ole Bob

New member
Some people say they are created under intence pressure, some say errosion or both.  Where would the pressure or errosion have started in water icicle?
It seems strange to arrive at that 3 way junction and the whole system apears to be a ridge on the surface??
 

Pitlamp

Well-known member
This has actually been discussed at length in a separate thread elsewhere in this forum (a bit of searching about should find it). The bottom line is that phreatic cave development is due to two main processes:

1. Chemical; the water removes limestone by chemically dissolving it since the calcium carbonate (mainly) which limestone is made of is slightly soluble in natural waters, the latter being acidic due to the absorption of carbon dioxide and organic acids collected from the soil.

2. Physical; moving water carries a sediment load (sand, gravel, pebbles and cobbles) which is abrasive (in the same way as the sediment erodes the floor of vadose passages underneath a fast flowing stream).

Until fairly recently I suspect that many people thought that most phreatic development was solutional - and they often suggested that perfectly formed phreatic tubes were caused by equal rates of solution in all directions. Direct observations by divers in phreatic passages have shown this to be over simplistic. Firstly, streams flowing in phreatic conditions transport often large amounts of sediment and even large pebbles can be directly watched bashing against the roof, floor and walls of submerged passages in high flow conditions. In other words physical erosion plays a major role in the removal of limestone. There is also the phenomenon of layered water which is commonly seen in underwater caves, where different layers have different chemistry and therefore very different aggressiveness. A further complication is the "mixed water corrosion" effect where different water layers meet.

The pressure in a phreatic passage is directly related to the depth below surface. Even before going underwater we are all subjected to a pressure of about 1 bar as we live under a "sea" of air which we call the atmosphere. But as one descends in water (which is much denser than air) the pressure rises fairly quickly. At a depth of 10 m the pressure is 2 bars. At 30 m the pressure is 4 bars. And so on.

In the Dales at least it is possible to estimate what the pressure was in now drained phreatic passages if their contemporary resurgence is known (because many phreatic passages are completely explored and are close to valley sides). Even if old resurgences aren't directly known it may be possible to predict their level from knowledge of previous valley floor levels between glaciations (if the age of a passage is known from dating stalagmites). I don't think any old resurgence draining Water Icicle is known though, so estimating the pressure which was once present in those tubes isn't very easy. But the pressure is a very minor factor and what matters is chemical dissolution and physical erosion.

Just out of interest, what are you wanting to find out?
 

Black Ole Bob

New member
I'm relativly new to potholing, done a few mines,  done a few pots, caves etc even some urban exploration, drains, sewers, flood passages that sort of thing.
But i can't stay away from the phreatic tubes, care what size they are, they are absolutley stunning!
They have been around for millions of years & man has only been here for a short time, But we've been lucky enough to find & explore them.
So back to your question, I would like to get a better understanding of them, why they occured, wich way they flowed, where they lead to etc.

Thankyou Pitlamp for your indepth replies, Are there any studies of them published? or anything you sugest i read?
 

4bags

New member
If you like phreatic tubes, go visit Bakerloo Straight in Dan Yr Ogof, arguably (it probably will be in this forum! o_O) one of the best in the country.... (y)
 

Pitlamp

Well-known member
Langcliffe is right; very few have been around for more than a few hundred thousand years. There are some (e.g. in the Peak District) possibly associated with early cave development at the time the carboniferous limestone was actually being formed (i.e. well over 300 million years!).

A very good place to start reading is the various BCRA Cave Studies series of booklets. If you really want to get in deep then there's some good stuff in the Cave & Karst Science journal but this is quite technical. There was a number of very good regional books published in the 1970s in the "Limestones & Caves Of . . . " series. If you can get at a good caving club library you should find these. If not, as a start, visit your public library and ask them to get the following 2 books to browse through:

Limestones & Caves Of The Peak District (Ed Ford, 1977) ISBN 0 86094 004 1
Limestones & Caves Of North West England (Ed Waltham, 1974) ISBN 0 7153 6181 3

Both were published by Geo Abstracts Ltd, University Of East Anglia, Norwich, NR47TJ. (All this information will help your library get these for you.)

Happy reading!
 

graham

New member
Langcliffe is correct about the age of our caves. Half a million years would take you back before most of 'em. A few rare objects are indeed older, but they won't (now) look much like the tube in peak Cavern or DYO's Bakerloo Straight.

I find Alfred Bogli's 1980 book , Karst Hydrology and Physical Speleology (translated from the German by June C. Schmid): Springer-Verlag, New York, 284 p. to be good on this aspect of cave genesis.
 

Les W

Active member
4bags said:
If you like phreatic tubes, go visit Bakerloo Straight in Dan Yr Ogof, arguably (it probably will be in this forum! o_O) one of the best in the country.... (y)
Along with the Peak Streamway downstream from Surprise View.  (y) (y)
 

Paz Vale

New member
Pitlamp said:
Firstly, streams flowing in phreatic conditions transport often large amounts of sediment and even large pebbles can be directly watched bashing against the roof, floor and walls of submerged passages in high flow conditions.

Has this process been photographed or even better filmed particularly the action of the pebbles bashing against the roof.
 

Brains

Well-known member
If not, then I suspect taking a trip into Peaks' Treasury during a major flood event and sitting at the bottom of the ladder by the sump would give plenty of opportunity to film this phenomenon.
 

Peter Burgess

New member
Paz Vale said:
Pitlamp said:
Firstly, streams flowing in phreatic conditions transport often large amounts of sediment and even large pebbles can be directly watched bashing against the roof, floor and walls of submerged passages in high flow conditions.

Has this process been photographed or even better filmed particularly the action of the pebbles bashing against the roof.
Imagine what sort of camera would be able to withstand such an onslaught!
 

Roger W

Well-known member
Peter Burgess said:
Paz Vale said:
Pitlamp said:
Firstly, streams flowing in phreatic conditions transport often large amounts of sediment and even large pebbles can be directly watched bashing against the roof, floor and walls of submerged passages in high flow conditions.

Has this process been photographed or even better filmed particularly the action of the pebbles bashing against the roof.
Imagine what sort of camera would be able to withstand such an onslaught!
Never mind about the cameraman!
 
Dear Sir,
I have once again found myself stumbling across this forum by means of  a simple overenthusiastic    misunderstanding when using this infernal new search locomotive thingy.
What I was intending to find was one of those 'Hot' phreatic action!! sites one hears so much about down at the club, what?

I remain etc......
yours.

Whatwotleigh.
 

Pitlamp

Well-known member
In reply to the question from Paz - I've never had the opportunity to film it but I've often thought of trying as I'm not convinced that our better known cave scientists really appreciate the role which physical erosion plays in the development of phreatic passages.

There is plenty of indirect evidence of this physical erosion though as well as reports by divers having watched it happening. There are erosion forms called "pseudokarren" commonly found in active sumps. These are vertical or subvertical grooves, usually on steeply dipping rock surfaces, caused by miniature "rivers" of sand cascading down them. (There is an article about this in an issue of BCRA Cave & Karst Science from a few years ago.) Where large phreatic passages meet restrictions (which speeds up water flow) the characteristic brown patina on the rock roof and walls is missing and clean, pock marked rock surfaces become evident. Also, there are "false" vadose canyons and rockmills on the floors of certain sumps which carry a fast current in high flow. (By this I mean they are formed in a similar way to those which develop in vadose conditions but these are formed entirely within the phreatic zone.)

Thinking about it - I'm sure there are videos of people cave diving in strong currents on you tube in which it's possible to see gravel & pebbles moving fast.
 

graham

New member
John

Did you read the paper in C&KS by Charlie Self & me a few years back Redefining the Boundary between Karst and Pseudokarst?
 

Duncan Price

Active member
Pitlamp said:
There is plenty of indirect evidence of this physical erosion though as well as reports by divers having watched it happening...Thinking about it - I'm sure there are videos of people cave diving in strong currents on you tube in which it's possible to see gravel & pebbles moving fast.

John is quite right.  In the early days of digging at Pwll-y-Cwm (the resurgence for Agen Allwedd/Daren Cilau) we would dive it in flood.  One could here the rattle of the stones from near the surface and at the bottom of the shaft rocks the size of a child's football would be bouyed up by the flow of the water though the choke.  I don't think that we ever filmed it but on several occasions when we couldn't dive we lowered an improvised underwater camera (John Stevens' camcorder in a reinforced ammocan with a window) and saw similar.

The comment about vadose-looking passage forms being found in sumps is interesting and further into this sump is a section very much like this - formed in a section where the sump goes up a ramp.

Duncan
 

cavermark

New member
Black Ole Bob said:
It seems strange to arrive at that 3 way junction and the whole system apears to be a ridge on the surface??

Such things go to show that a lot of phreatic systems (and other cave passages) bear no relationship to the current surface. The top of Titan being under the top of a hill being a good example. Presumably the water icicle shaft was picked out when t'owd man had another way in to the cave to know where to put it..
 
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