Easier ways to discover new cave passages!!!

[Antony B]

"I believe resistivity is just not going to give you a useful answer."

Completely and utterly untrue. If you read standard texts relating to the subject of geophysics (e.g. An Introduction to Applied and Environmental Geophysics by Reynolds 1997, Applied Geophysics by Telford et al 1990) or up to date articles on the subject (Integrated geophysical surveys applied to karstic studies by McDonald, R. & Davies, R. 2003. First Break) then you'll discover that Electrical Resistivity Tomography is commonly used in every day geophysical surveys, often specifically for reliably detecting voids to a depth of 30-40m. Case studies including results can be seen on the TerraDat website.

Resistivity techniques are based on sound mathematical principles that have been continuously proven by intrusive investigations such as boreholes, unlike dowsing which really is a subject of speculation.

 

[Ouan]

Agreed. There was a complete debunking of this by J.O. Myers in Cave Science (Vol 2 (4) pp 167 - 172) in 1975. The article is entitled Cave Location by Electrical Resistivity measurements: some misconceptions and the practical limits of detection

I suspect that resistivity equipment and techniques have advanced in the past 30 years, seismic certainly has. Are there any recently published studies which used modern kit? Is Myers' paper still relevant?

There is a small display in the Shepton hut showing the resistivity lines plotted over the survey of Lamb Leer and the fabled 'Palmer's Chamber'. It's very colourful.

 

[andymorgan]

Agreed. There was a complete debunking of this by J.O. Myers in Cave Science (Vol 2 (4) pp 167 - 172) in 1975. The article is entitled Cave Location by Electrical Resistivity measurements: some misconceptions and the practical limits of detection

I like to have a look at this article to see its reasoning. However I don't hold out much hope of it having decent conclusions, is it a proper 'peer reviewed publication' and what is its impact factor (I couldn't find one on the journal citation reports)?
However is there any evidence it works to the contrary in a peer reviewed journal...

EDIT
oops a bit slow writing, so didn't see some of the above posts before writing

 

[graham]

One could argue that the kit had improved between Palmer doing his Lamb Lair work for the first time in the 1930s and the second time in the 1950s, but the results didn't improve. You can improve the kit as much as you want but if the fundamental principles were erroneous then they remain erroneous now.

I wrote a piece in the Pengelly Newsletter in 1992 which showed that the only caves that Palmer "proved" to exist were those that he already knew to exist. None of the "new" caves have ever been entered.

 

[Ouan]

You can improve the kit as much as you want but if the fundamental principles were erroneous then they remain erroneous now.

This has been answered by Antony B

One could argue that the kit had improved between Palmer doing his Lamb Lair work for the first time in the 1930s and the second time in the 1950s, but the results didn't improve.

In what way did the equipment improve between the 1930s and 1950s? Computing advances since Myers' 1975 paper mean data can be collected and processed in quantities and speeds that were not possible 30 years ago.

None of the "new" caves have ever been entered.

Has anyone dug or drilled into the location of a 'Palmer Cavity' to prove that he was wrong? Or is it just that cavers haven't put enough effort into their digging?

 

[graham]

Well, the MNRC & others spent a long time trying to extend Lamb Lair in the direction of Palmer's Chamber & Pete & Alison Moody similarly dug for quite some time in "Palmer's Rift" over near the Tynings Riding Stables. Neither reached anything like what Palmer had predicted.

 

[Antony B]

The survey technique that Prof Palmer used was resistivity traverses and the interpretations were based on curve matching. The result between 1930 and 1950 basically improved because Prof Palmer was able improve the mathematical theory behind the technique.

During the 1990 large advances were made in improving the technique further due to the significant introduction of computers. Nowadays resistivity tomography is used which involves an array of regularly spaced electrodes along a survey line connected to a central control unit via multi-core cables. Resistivity data are then recorded via complex combinations of current and potential electrode pairs to build up a pseudo cross-section of apparent resistivity beneath the survey line. The depth of investigation depends on the electrode separation and geometry, with greater electrode separations yielding bulk resistivity measurements to greater depths.

Measured apparent resistivity data are plotted initially as a ‘pseudo-section' image which means that the measured values are only apparent in terms of magnitude, location and depth. The modelled true subsurface resistivity image is then derived from finite-difference forward modelling. Provided the air filled void is of a detectable size then it will be represented on the image as a very highly resistive anomaly as in theory the resistivity of air should be infinity.

Significant work has been put into locating 'Palmers Chamber' however if it exists then there's been no luck as yet. The work that i'm doing is trying to investigate if his result were right with the hugh advantage of recent developments in the technique. Even though Palmers work was at the beginning of the techniques development he did have success with his work at Pen Park Hole.

 

[graham]

... Even though Palmers work was at the beginning of the techniques development he did have success with his work at Pen Park Hole.

Aha! Wrong. At Pen Park Hole, Palmer had the advantage of having White's 18th century survey. He already knew exactly where it was and what shape it was.

 

[nickwilliams]

That's a thought - set off a big enough explosion to detect the possible cave beneath and voila - you create your own cave (albeit more of a large shakehole)! :wink:

When I did my digging apprenticeship (I majored in Squalor at the Faculty of Sparks and Chemicals, University of Ingleton, under (occasionally, but more often just in front of) Prof. Bob 'The NCC diplomat' Molephone)) we had a theory that the best measure of passage size was a case of bang. You pushed it in with your foot as far as it would go, and when it got jammed, the passage was clearly too small and so the match should be applied to the fizzy fuse.

Then there was a theory which involved turning limestone to Blancmange (sp?) and employing a trailer load of rats to eat the passage open. I forget the details - I seem to recall a large volume of Theakstons cooking bitter was also involved, but it's all a bit hazy now.

Nurse! I'm hearing the voices again!

N.

 

[AndyF]

"I believe resistivity is just not going to give you a useful answer."

Completely and utterly untrue. If you read standard texts relating to the subject of geophysics (e.g. An Introduction to Applied and Environmental Geophysics by Reynolds 1997, Applied Geophysics by Telford et al 1990) or up to date articles on the subject (Integrated geophysical surveys applied to karstic studies by McDonald, R. & Davies, R. 2003. First Break) then you'll discover that Electrical Resistivity Tomography is commonly used in every day geophysical surveys, often specifically for reliably detecting voids to a depth of 30-40m. Case studies including results can be seen on the TerraDat website.

Resistivity techniques are based on sound mathematical principles that have been continuously proven by intrusive investigations such as boreholes, unlike dowsing which really is a subject of speculation.

I've just spent two years writing software that models water infiltration into soil layers, and the corresponding recharge into sub-soil geological layers. we also used models for saline intrusion near coastlines. I read lots of "papers" published by researchers, and high proportion of them contained psuedo maths that was impossible to verify or tried to provide a generilzed theory based on a specific catchment model. Other parts were just plain wrong. The conclusion I reached was that a great proportion of mathamatical modelling used in these areas is bogus... so the fact that a paper is "published" carries no weight for me.

I'm also very familiar with the maths of Tomography (albeit Circular rather than Plane Tomography).

What I want to see is evidence - show me the graphs, plots and data, and describe the conclusions that have been reached. I shall look up the quoted references, and report back....

 

[AndyF]

In what way did the equipment improve between the 1930s and 1950s? Computing advances since Myers' 1975 paper mean data can be collected and processed in quantities and speeds that were not possible 30 years ago.

I don't think the equipment has improved. at the end of the day you are measuring resistance between any two points. The key improvement is in the maths, and application of tomographic techniques should give "better" results, but the limitation of the data is still the overridding factor, and the domination of "noisy" surface layers is always going to severly limit the process IMHO.

 

[AndyF]

Here is the reference...

http://www.terradat.co.uk/firstbreak.pdf

 

[cap n chris]

http://www.writewords.org.uk/news/436.asp

 

[graham]

http://www.writewords.org.uk/news/436.asp

:?:

 

[cap n chris]

Graham, it's just a link to a page about cliches such as "At the end of the day" which was FULLY WORN OUT as far back as 1994 but still keeps being used as though it's fresh as a daisy, if you know what I mean, at this moment in time, when all is said and done, etc. etc. etc., etc. FFS

 

[graham]

OK mate, it just wasn't clear what you were criticising.

 

[cap n chris]

Sorry, I'm calm now; and rather than being a criticism I wrote more in the style of an observation but suppose it's my problem rather than anyone else's since these TINY things nag at me. I probably need therapy.

 

[Antony B]

My intention in posting a description of the work that we are carrying out over at Lamb Leer was to provide information to questions that have been asked in this discussion. As a practising geophysicist working for one of the main specialist geophysical companies in the UK i spend my working life overlaying borehole results on the resistivity datasets that i have collected. The two data sets always tie together. As i have repeatedly advised, results of geophysical techniques can be seen under case studies on the terradat website. I can however see that if you've had no training or experience with the subject then it can be viewed as a magical science.

Obviously work carried out at the birth of the subject should be treated with some sceptisism but principly because the subject was in the very early stages of development. This does not however entitle Prof Palmers work to be completely discredited by claiming that he 'forged' his results through basing them on 18th century surveys.[/quote]

 

[AndyF]

Hi Antony,

Please don't interpret my comments as critical and/or dismissive - they aren't meant to be. I'm keen to see a lively debate and what this thread throws up... I've done a lot of Geophys modelling software (notably with MODFLOW), and my qualifications are as an electronics engineer...

My "challenge" still stands, can we see some profiles/plots from your Lamb Leer work. This is an ideal opportunity to see if the predictions match the ultimate reality. So often techniques are claimed as a success after interpreting discoveries and results after the event....

 

[graham]

Obviously work carried out at the birth of the subject should be treated with some sceptisism but principly because the subject was in the very early stages of development. This does not however entitle Prof Palmers work to be completely discredited by claiming that he 'forged' his results through basing them on 18th century surveys.

Ahem, I did not say that Prof Palmer forged anything. I simply pointed out that in the case of Pen Park Hole he used the technique to confirm the presence of a cavity at an already known location.