It is generally accepted that the "depth" of a cave is the vertical distance from the highest point in the cave to the lowest point. This is normally not the actual depth that you are underground, just a value to show the vertical extent of the known cave system.

I have often thought it might be more interesting to know the depth relative to the surface directly above, in certain circumstances. And with modern digital mapping tools of the surface it is now getting much easier to actually calculate this.

So this then begs the question, "What is the "deepest" bit of cave in the UK, or even the world for that matter...?" 

I don't know, but wherever it is, it's bound to be in Derbyshire.... 

The deepest potential in Mendip is Wigmore to Goughs.

The very bottom of Main Rising in Speewell must be a contender. It certainly feels very deep! The far end of Black Keld must be getting pretty deep under't sod as well.

Rob said:

I have often thought it might be more interesting to know the depth relative to the surface directly above, in certain circumstances. And with modern digital mapping tools of the surface it is now getting much easier to actually calculate this.

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This is similar to a question I posed a while ago, when I was looking for locations for testing cave radios; that is, where are the locations where the surface is the furthest away, in any straight line. Obviously quite lot of supposedly "deep" caves could actually be quite shallow because, although they might sink high on a moor, they might terminate close to a resurgence. I didnt do any particularly serious or diligent research, but enough to produce a rough list of Dales caves in CREG journal 18 (December 1994).

The deepest in the Dales was, I guessed, a location in Dowbergill passage because, although the passage between Dow Cave and Providence Pot doesnt actually go very deep, Great Whernside rises above it, and so you can go 200m "deep" without actually descending very much.

If you avoid diving (and so you dont include Deep Well sump in GG at -195m, including -40m of dive) then the next deepest was, I thought, Meregill Hole, -172m at the bottom of the last pitch. But if you go along the Main Drain that takes you into a shallower zone because of the surface terrain.

All the other Dales locations I looked at were much shallower than 200m, and several did not actually involve much vertical caving. For example, Hall of Justice in the Sleepwalker series of White Scar Cave is up to 140m deep due to the surface terrain rising above it, and Valley Entrance in Kingsdale Master Cave is up to 90m deep as you walk in, under the hillside, to a location somewhere near the Master Junction.

Im told that North West Junction in Agen Allwedd is at -192m and that White Passage in Daren Cilau is at -198m, both of these allowing for the sloping surface terrain.

I would be interested to know of any other UK sites that are as deep, or deeper than these, especially if they are easy to get to

I think Titan to Speedwell streamway is over 200 m, before even diving into Main Rising.
(Would have to check . . . . )

The very end of the final Wookey sump is a long way below surface too.

Pitlamp said:

I think Titan to Speedwell streamway is over 200 m, before even diving into Main Rising.
(Would have to check . . . . )

The very end of the final Wookey sump is a long way below surface too.

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Wouldn't Moose's survex model tell you? Nettle to Deep rising is over 300 m & I reckon that's the best bet in the UK for this particular stat.

Ok, I've looked at the figures and I get this:

The deepest bit in the Peak system is indeed the bottom of Main Rising which is 266m below the entrance of JH (almost directly under it as a matter of fact).

The deepest potential is somewhere under the Mountbatten Pot area, where if you were unfortunate enough to get to the water table and then swim to a point equal to the depth of Main Rising (I'm so glad this is theoretical) you would have 309m of the best bit of limestone in the UK above your head......

Pitlamp said:

The very end of the final Wookey sump is a long way below surface too.

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Overlaying the Wookey survey on Google Maps suggests that the surface directly above the end choke* is about 250 m AOD.  The resurgence is at 70 m AOD which puts the depth of the rock at the end around 270 m.

* 600 m due south of Templeton Mine.

Impressed, I would have guessed about 20 m or so less than that for Wookey.

For caves where the data has been kept in Survex, Mike McCombe's program at http://uk.geocities.com/mikemccombe@btinternet.com/terraintool.htm might help visualise the position.

That won't work for Wookey, of course.

My overlay shows 220.5m O.D. for the end of wookey and the resurgence at 61 O.D. taking the sump depth as -90m the depth of rock would be nearer 250m and 160m for chamber 25.

Come on guys........get your facts right! :read:

How thick is the limestone over the end of DYO?

exsumper said:

My overlay shows 220.5m O.D. for the end of wookey and the resurgence at 61 O.D. taking the sump depth as -90m the depth of rock would be nearer 250m and 160m for chamber 25.

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The MCRA website has the altitude of Wookey Hole as 70 m O.D.  This is probably the showcave entrance which ties in with the resurgence being at 61 m then (this figures with the prime survey point in 9 being at 62.67 m O.D being the rock to which the upstream line is tied). Does you altitude for the surface above the end take into account the 230 m of passage beyond Parker's limit?  This is 400 m W and 625 m N of the PSP and puts the end further under the hillside - on the OS map it looks like it clips the 255 m contour.

Depth at end = 255 - 61 + 90 = 284 m

Do I get full marks for showing my working out?

Duncan Price said:

* 600 m due south of Templeton Mine.

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It's not a fecking mine.  Twot(s).





Apologies - off topic.

Hughie said:

[It's not a fecking mine.  Twot(s).

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if it walks like a duck and quacks like a duck.....

Thats where the discrepancy lies duncan. The reference is for the show cave entrance, also my survey only goes to parkers limit.

Th deepest bit of Dan Yr Ogof looks to be the Great North Road, this is at about 260-270m with the surface being at 460-470m giving it about 200m depth.

The cave passage rises towards the the Far North Choke, here the passage is at 320m with surface at 500m.

exsumper said:

The deepest potential in Mendip is Wigmore to Goughs.

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Or Battery Swallet

If the wookey terminal sump continues at -30 O.D. towards templeton at 252 O.D. the depth below the surface will be 282mtrs  which is potentially the deepest passage below surface level on mendip.So if the templeton diggers manage to intersect it, they will also have the deepest mineshaft on mendip. two records in one.