Sandy Hole - North Passage

tim.rose2

Active member
A new dig, well actually a very old one revisited...

North Passage in Sandy Hole is essentially the continuation of the entrance phreatic tunnel beyond the inkwell. This would have been an isolated phreatic running approx. 4 ft above the main North-South Passages in the cave had the bottom not fallen out of it where it intersects Gold & Silver Passage to create a junction. To demonstrate the point, only a few metres further ahead, North Passage passes directly over Paul's Progress. The vertical distance between the two can only be few inches, yet when in either passage you are blissfully unaware of the others existence. Until yesterday, North Passage ended at a calcited choke where it had been intersected by a much younger mass movement rift 26 m North East of the Inkwell, heading inland (shown on the survey below). 12 m North of North Passage is another small phreatic (Shitzentrasse) heading in a similar direction also ending choked at a rift on a similar longitude - presumably the same rift.

North Passage is an arduous flat out crawl varying from 3 to 5 ft wide, ending very cramped with little to no stacking space along it's entire length. The terminal choke consists of calcited infill. The Hardye's School CCF briefly had a go at digging this in the early 1970's not long after its discovery but made little progress due to the cramped conditions and loosing interest upon discovery of Ariel cave in 1974. Inevitably the choke would only be the width of the rift (approx. 2 ft), however as this is near the bottom of the limestone and the rift probably extends 20m above - like a good game of kerplunk, remove the wrong stone and there's a good chance of bringing down a lot of debris, making it a very long 2ft! To my knowledge, nobody has tried to dig North Passage since the 1970's and I dare say few have visited either.

The interest is fairly obvious - a downstream water worn passage, heading inland into an area beyond all known passages. The water obviously went somewhere and there's zero chance of that being a resurgence without crossing the entire island. Furthermore the existence of Shitzentrasse a few metres North gives hope the two passage will unite, as is seen at the confluence in Ariel Cave, resulting in an enlargement. Extrapolating further, wouldn't be it nice it they flowed into another (larger) inland North - South passage! This is very much one of those places that had it have been in a major caving region would have been pushed to a conclusion decades ago.

Sunday 5th Jan, myself and Dan set off to the end of North Passage to determine if there's any hope of passing the choke. Several knackering hours of mostly hammer and chisel work in an extremely constricted space, and at the point of more or less exhausting the limited places we had to loose spoil, we managed to open a small hole through the choke providing a view of the continuing passage. We were both too knackered to do anything about it so it had to wait until yesterday. Saturday 11th Jan - Mike K kindly agree to a trip to push the end with me on the promise of a certain breakthrough... It took Mike about 20 mins to enlarge the hole through the choke to a size we could pass but he was met on the far side with an extremely frustrating passage... Not quite big enough. The phreatic was approx. 18 inches high, 4 to 5 ft wide (sounds good) but with a 6 inch layer of extremely sticky mud in the floor and occasional rocks from either ceiling collapse or that had dropped down narrow rifts making easy progress impossible. If the passage was 6 inches higher or the mud not present we've have simply crawled ahead. Instead Mike spent the next 3 hours channelling a route through by pushing mud and rocks side ways whilst I followed behind further enlarging and improving the stacking to maximise space. We reckon we've more of less doubled the length of North Passage in doing this, perhaps adding around 20 m beyond the end shown in the survey below. The passage is still going, wide and low and more of the same with a view to another small collapse a few metres ahead. No sign of picking up Shitzentrasse yet or the passage growing in size. We've decided dragging spoil back the entire length would be near impossible so we'll continue over the coming weeks and months until we either find something, there's too much spoil to push aside or we need the drill. Sandy hole has already got enough horrible passage and we've just added another 20m with the prospect of more pretty high! The problem with these damn phreatics on Portland is that they tend to go a long way - if this one doesn't improve I'm certain we'll soon get bored with it.

I'll update this thread as the dig develops.

If anyone wants a dig - Shitzentrasse is up for grabs. I suspect it'll be exactly the same and probably lead to the same place ultimately.

Sandy Overlay 2.jpg
 
It's been a few months since my last visit, but I finally found some willing volunteers yesterday to come to North Passage. Two aims, firstly to survey and secondly to push the end. I'm happy to admit that volunteers for this one are lacking, but we've also been working on a master survey of the West Cliff caves and also busy doing other things, so the hiatus isn't just due to a lack of friends!!!

Anyway, Mike R and Sean were issued crowbars and set off to make the end of the passage further away. Mike took the lead pushing ahead whilst Sean tidied up behind. I surveyed the passage, created a 'turning circle / passing place' and then followed Sean, sweeping the floor to gain every millimetre possible. The passage really is quite hideous to move along and required significant contortionism to survey it. Getting my head and arm aligned so that I could see the next / previous survey point without having bits of body or leg blocking the view was quite tricky! One does wonder what the f**k am I doing? That said, it's got a rather attractive, curved, water worn ceiling with immature bits of calcite and frequent hanging chert nodules. I'd like to get some photos' but there's a lot of mud in the floor and I suspect I'd just kill the camera trying. Having surveyed to the end of yesterdays session (which added around 12 m) we're now 32 m from the former passage end. Not bad for two sessions.

As for the current end... We've left it with a view of a rubble slope about 2 m ahead and possibly something off to both the right and left of this. The rubble looks to be loose infill which has probably come down a rift (thankfully no flowstone in sight as that stuff makes life much harder). It all looks very promising but it'll need another hour's work to determine that. We all obviously hope the rift (if that's what we've found) is big enough to fit into and with any luck might provide some space for spoil / standing up etc. The main thing is that it looks different and that gives us hope it's not just simply more of the same. The bad news is that if it is a rift we've found the tunnel probably continues exactly the same beyond!

North Passage is still heading inland, approximately west to east which is unusual on Portland, and yesterday had a decent draught which must be coming from somewhere. The latest survey is below:
North Passage 18-05-25.jpg


All I need now is some friends again and with any luck the next exciting instalment will follow!
 
The final instalment from North Passage....

Sean and I returned today seeking glory and instead found the end! Sean led the way, clearing the route to reach the rubble slope observed ahead at the end of the previous session. Unfortunately what we found was a large volume of debris lying at the bottom of a wide rift. Poking upwards approx. 1 m (that's all I could safely achieve with a short crowbar) showed no end to the (very loose) fill vertically. As for the water worn tunnel that seems to turn right handed and follow the route of the rift rather than crossing it. This, in short, means the phreatic has been annihilated and the remnant filled as the rift opened. Attempting to following the route of the tunnel, for the next few metres at least, would likely be impossible to dig; as soon as you remove material another load from above would appear. The rift looked as though it would be plenty big enough to yield passage if sufficient infill could be cleared to provide a route upwards (assume there is something open up there) but there's zero stacking space and I've zero interest in attempting to pull a sh*t tonne of debris back 65m to the start of North Passage. There's no chance of using a drag tray so it would be a case of filling tackle sacks and doing 130 m round trips, which would probably take 30 to 40 min each. So we've decided to declare this the end of North Passage.

I did have a poke around the floor beneath the rift hoping a void might appear to chuck the spoil in, but no such luck.

What we have achieved is adding 35 metres of truly awful passage to Sandy Hole in 4 sessions; in normal fashion for Portland we've therefore made the cave both longer and worse! I shall declare North Passage a collectors item!

I did take a couple of poor photos whilst Sean was doing all the hard work...

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The only remaining bit of interest in North Passage is the rift we first passed (i.e. the old end). This rift looks wide enough to yield passage and there is a small hole through which you can see what looks like open space about 1m above. If the on-going water worn passage was sacrificed, or at least made very small it might be possible to loose enough spoil to be able to enter this one. The advantage with this rift is the infill is cemented together with calcite, so it's much easier to control the volume of spoil you're creating. The downside is that it'll need drilling. I may return at some point to look at this, but otherwise I suspect I may never visit North Passage again.

Onto the next site then!
 

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