Author Topic: A new cave for Portland  (Read 4224 times)

Online tim.rose2

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A new cave for Portland
« on: July 15, 2018, 11:23:09 pm »
With not a lot to do and no friends, Saturday I headed off to Portland to visit my Mum.  During the afternoon I decided I'd go out for a "walk" and headed off up the cliff, descended via the climbers path to the crag called the Veranda, dropped down to the boulder beach and hopped along to the Coastguard path at Portland bill.  The hidden agenda was to see if it was possible at low tide to get to a sea cave I've been wanting to visit for a while.  The answer is yes, but not without getting salty wet feet so decided to leave that for another day having had a little excitement already...

Along the way I spotted a feature of interest!  What appeared to be a possible (but blocked at about 2m in) phreatic entrance.



Obviously I felt inclined to move a few rocks and that lump of tree washed in by the sea to get my arm and camera through a gap.  This was the result...



With no caving kit and nobody really having any idea where I was further poking was going to have to wait.

Strangely enough my suggestion to Sas for what to do on Sunday was to take the crowbar, some caving kit and head back to my blocked hole.  Having negotiated the 'path' to the entrance we started shifting boulders and within 15mins we had a route through into the void seen on the image above.  It was now apparent this was definitely a phreatic tunnel rather than something undercut by the sea.  A further minor blockage about 8m in was cleared within 10 min and we crawled into the open passage beyond.  The passage is typically 1.5 m wide varying from roughly 0.4 to 1 m in height.  We explored to approx. 50m passing some nice but very vulnerable formations.  Despite still being open, we didn't have time to crawl further on this occasion however it did look as though the tunnel continued but a little more boulder shifting might be necessary.  More next time!

The details...
The cave is in Wallsend Cove which is on the West side of the isle but much further south than any known pheatic passage on Portland (please correct me if you know differently).  As far as I'm aware this cave has never been reported before (again please correct me if you know differently).  I'm pretty certain the cave is in the same band of rock as Sandy Hole, Hopeless Hole & Showerbath approx. 1.3 miles to the North.  Could this be the other end of Ammonite Passage?  The tunnel dimensions are similar.

Unfortunately this cave could well answer a long standing question of the end of Ammonite Passage - is it tidal?  This cave is roughly level with the high tide limit and I don't doubt it floods on spring high tides (we were there at low spring tide today).  In anything other than calm seas, the cave would also be a death trap.  Numerous bits of sea detritus are deposited throughout the cave including as far as our limit of exploration today, which was the far side of two boulder blockages.  As a result I strongly advise you do not attempt to visit unless you fully understand the tides and weather.  I'm also guessing each time there is a major storm the entrance will need clearing.

Our trip did include a little humour when I lobbed "the remains of the last caver who attempted to explore this cave" at Sas - a manky old welly washed in by the sea!  As a result we've decided to name it "Wellington Hole".

A few pictures...

Sas coming through the second blockage:


The passage beyond:


A lower bit:


The wellie:


The entrance:


Well it just shows an hour of effort moving boulders by hand can find caves.  I could really do with more friends - I think this is now the 5th promising site on Portland I'm poking around with.

Offline pete h

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Re: A new cave for Portland
« Reply #1 on: July 16, 2018, 03:30:29 pm »
Hi Tim.  Have a word with Nigel Graham he knows a lot about Portland, you can get his details from the Wessex membership list or if needed i can pm them to you.
Pete.

Online tim.rose2

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Re: A new cave for Portland
« Reply #2 on: July 16, 2018, 04:09:07 pm »
Hi Pete,
Already in touch with Nigel, but thanks for the suggestion.
Tim

Offline NigelG

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Re: A new cave for Portland
« Reply #3 on: July 16, 2018, 06:43:16 pm »
Indeed - Tim passed me the link to this!

The rather remote location (for Portland), and the world's oceans, may well be why this is a new find. I have sent a message to Mike Read, with a copy of the link, to see if he knows anything about it, but I don't recall him ever telling me of caves like this that far South along Westcliff.

I've searched too, but fruitlessly, apart from one tiny "cavelet" really only an anastomosis channel.

Even the mass-movement rifts thin out Southwards as the cliff is much lower and less over-steepened.

There are vague traces of phreatic development right at The Bill, but nothing of enterable size; and there are or were some phreatic tubes in an old quarry NE from the Lobster Pot Café and beach-huts. These were only partially silted up, and the largest might - very "might" - have yielded to a very slim digger, but I've not found them recently and think them now buried by debris.

No water-worn features reported from any of the quarries South of Southwell village, either, though the old ones along the cliffs are too shallow to have found the deep-lying caves like Sandy Hole and Tim's discovery. Sandy Hole is near the base of the Cherty Series or even in the Basal Shell Bed, so not far above the bottom of the limestone sequence.

So if no-one else has any prior knowledge, Congratulations Tim, and although bearing in mind the tidal dangers, this one might yield a lot of passage....

Online tim.rose2

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Re: A new cave for Portland
« Reply #4 on: July 20, 2018, 08:48:23 pm »
Today myself and Richard headed to Wellington Hole at high tide (1.5m above datum) to have a look at whether access into the cave is possible with this level of water.  The good news is yes, however you'd not want much more water.  We think the entrance would be partly flooded on a high spring tide. 

Having been granted access by the sea gods we decided to see just how far we could get.  We arrived approx. 1 h before high tide with only a further 10 to 15cm rise in sea level expected before turning at 1:15pm.  The passage was completely dry as far as myself and Sas got last weekend.  Naturally we continued into virgin passage.  Typically the passage was 1m high and about 1.5m wide so quick progress on our hands and knees was made.  No further boulder clearing was necessary.  After a while a small pool was found in the floor, which was quickly followed by larger flooded area.  We sat there for a few minutes and watched the water level rise by a couple of cm's as it appears to flow towards us and then stop.  A short flat out crawl along the mud bank adjacent to the pool gave a view of the ceiling lowing into the water.  We have found what appeared to be a tidal sump (oh goody)!  Closer inspection of the ceiling clearly shows this area floods to the roof regularly in contrast to the earlier parts of the cave.  Presumably on springs as it certainly wasn't going to happen today. Interestingly, first appearances suggest the water was flooding towards us from further back in the cave.  We saw no evidence of it being below us and simply surfacing at this point.  This suggests to me there is another entrance below sea level somewhere.

This was clearly the end of exploration today so we headed back to the entrance - no new watery areas observed on our retreat.  Unfortunately we've not found any side passages and the only cross rifts are to small to fit in.  We estimate the length of the cave today at 120m.  When we measure it, it'll be interesting to see how far wrong we are.

So in conclusion, the cave entrance might well be ok at most states of the tide, however further back there is clearly a tidal death trap.  Do not go in here if you do not understand tides.  I am more than happy to advise.

Some of us will be heading back tomorrow a couple of hours before low tide to see how much further we can get with the intention of being well out of the way before the tide turns.  We'll also get out the tape measure out and determine the actual length of passage found.  The cave is completely linear heading roughly East.

Unfortunately I destroyed the current caving camera in another hole earlier in the morning so no new photo's today.  More tomorrow.

If there is anyone reading this with experience of tidal sumps (I only know of Otter - are there others?) I'd quite like a chat.

Offline mrodoc

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Re: A new cave for Portland
« Reply #5 on: July 20, 2018, 10:55:39 pm »
I wouldn't be surprised if this proved to be downstream Sandy Hole. I think the way to approach a tidal sump is to go in on a falling tide and, if it opens well before low tide, then you have a safe hour or two to explore. That is a lot of passage to negotiate if you are lucky enough to find it! Poses the Jrat awards team a problem as it is an outlier but currently would be a contender.

Offline Kenilworth

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Re: A new cave for Portland
« Reply #6 on: July 20, 2018, 11:37:21 pm »
Looks like a beautiful little cave, and reminds of the sort of caves I started in (and continue in, when I have the chance). I hope you enjoy it!

Online tim.rose2

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Re: A new cave for Portland
« Reply #7 on: July 21, 2018, 10:34:24 am »
Quote
I think the way to approach a tidal sump is to go in on a falling tide and, if it opens well before low tide, then you have a safe hour or two to explore.

That's precisely today's plan.  We'll be heading there around 5pm with low water at 7pm.
Unfortunately It's neap tides this weekend so we may have to return at springs should nothing open today.

Quote
Poses the Jrat awards team a problem as it is an outlier but currently would be a contender.
I know others will disagree with me on this, but having grown up on Portland, began my caving life as a Portland caver  (there was quite a few of us unknown to the outside caving world) and visited Mendip & Devon as "another region", personally I do not see Portland as an extension of Mendip nor is it in Somerset or Scotland.  As much as I would be honoured that Wellington was considered for any prise, I think the answer to this is simple - Would a cave found in Devon Count (i.e. a neighbouring region in a neighbouring county but outside of the scope originally published)?  So probably a simple No.  The other consideration perhaps - did Tony ever dig on Portland?

I'm beginning to question the proposal of Wellington being the end of Sandy Hole and now think it's most likely a tributary leading to it.  Although the passage appears horizontal, yesterdays observations clearly show we're heading downhill.  We're also heading in the wrong direction (roughly East).  I'll try to remember to have a look for some scalloping to determine the direction of flow today.

Offline andrewmc

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Re: A new cave for Portland
« Reply #8 on: July 21, 2018, 05:36:00 pm »
CSCC cover both Mendips and Portland but not Devon though; using one definition of the term Portland and Mendips are in the same region (which does of course not mean anything for the J-Rat awards).

Perhaps it is time for dedicated diggers of Portland to cast off the shackles of CSCC tyranny and strike out in a new shining era under PFPC (People's Front of Judea Portland Caving)...  :bounce:

Also, I used to climb on Portland; I'm keen to read the next installment! :)

Online tim.rose2

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Re: A new cave for Portland
« Reply #9 on: July 22, 2018, 09:46:52 pm »
Successful day Saturday...

Following an afternoon in Showerbath (I'll update that thread shortly) myself, Sas, Nick & Sam headed to Wellington Hole for an evening trip over low tide.  Several questions outstanding have now been answered.

1. We've found the end.  In fact myself & Richard had more or less found the end on Friday.  At low tide it's much clearer.  The roof drops down a little in a mucky, sandy watery slurry (the dregs of the previous high tide).  Nick decided he needed to make full acquaintance with the end so crawled on in the last few metres of the cave returning wet and mucky!  He also reckoned there was an air space between the sandy, watery slurry and the roof but was too small to proceed.  Given the size of the passage I don't doubt it continues amongst the silt, however with a daily flood to undo any effort, digging here in my opinion would be pointless.  Furthermore I can't see any prospects beyond achieving a few more metres in grotty conditions until the low water tidal limit is met.  Happy to take opinions from others on this - particular if there is anyone with experience of digging a tidal sump.

2. We now know the length of the cave - we've measured it to be 150m to the point it becomes rather unpleasant.  I'm sure some mad person could partially bury themselves in sand, licking the ceiling as they go to achieve another 5m if they wanted!

3. The cave is linear and (having taken a compass) heads SE at 140 °.  There are no cross rifts or side passages big enough to fit in.

4. We believe this is a tributary passage rather than the end of Sandy.  I'm no expert on such things but the few bits of scalloping I looked at suggests the water previously flowed inwards.

5. Now we know where the end is, I would suggest the cave will be safe to visit from mid-tide to mid-tide across low water irrespective of the size of the tide.  Calm seas are are essential, however if it's too rough for the cave then I don't think you'd get as far as the entrance anyway.  The obvious time for a trip should anyone want to, is from 2 to 3 hours before low tide.  A crawl to the end and back shouldn't take more than an hour even if going slow.  If anyone decides to start pushing the end then you'll need to consider the tides more carefully.

Some photos:

This is taken about 20 m before the end of the cave, looking ahead.  It's a thoroughly miserable place.  Just beyond this the floor becomes 'sandy' for the entire width and you are able to crawl until the slop nearly meets the ceiling (or just look at it from the last dry-ish point).


An entrance shot with Nick as our model


Various shots along the length of the cave






Formations - well there's not much.  Some of the roof is quite attractive.  There's a few stals and one calcited block.  Orange as per normal on Portland.





Sas with the welly


Sam emerging from the entrance stating how impressed she was with the discovery and explaining how she would be happy to go back anytime.


Finally a group photo afterward


If anyone does decide to visit, it would be good to see your thoughts / a trip report and perhaps some photo's posted here.

Online tim.rose2

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Re: A new cave for Portland
« Reply #10 on: July 22, 2018, 09:54:19 pm »
Perhaps it is time for dedicated diggers of Portland to cast off the shackles of CSCC tyranny and strike out in a new shining era under PFPC (People's Front of Judea Portland Caving)...  :bounce:

Both the People's Front of Portland Caving and the Portland Cavers People's Front (which is just down the road) have existed for a long time.  Over the years I've been involved with Portland Caving (since about 1998) there's been a lot of cavers and caving going on with little contact to the outside caving world or even communication with each other.  From conversations I've had I believe this goes back much further too. 

Offline mrodoc

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Re: A new cave for Portland
« Reply #11 on: July 23, 2018, 06:21:15 am »
Any evidence of marine life in the cave?

Online tim.rose2

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Re: A new cave for Portland
« Reply #12 on: July 23, 2018, 11:21:01 am »
An interesting question and one I've not really considered.  I can't say I noticed anything of particular interest.  There is evidence of what I'm assuming are Rats within the first 10m of the cave (bits of shit lying around).  I've also seen along the length of the cave the hind leg from a crab, a cuttlefish and plenty of rotting seaweed - presumably all washed in by the sea.

Offline mrodoc

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Re: A new cave for Portland
« Reply #13 on: July 23, 2018, 01:52:59 pm »
sometimes you get small beasties coming up through the cracks in anything tidal. They certainly do at Brixham.

Online tim.rose2

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Re: A new cave for Portland
« Reply #14 on: July 23, 2018, 09:56:52 pm »
There's certainly insects, flies and the such in there - gorging out on the rotting sea weed & rat poo.  Am I selling this cave?

Didn't notice anything sea related though.

Online tim.rose2

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Re: A new cave for Portland
« Reply #15 on: July 23, 2018, 11:09:02 pm »
I've updated the Portland Caves website to include a Wellington Hole page & added the location to the map:
https://sites.google.com/view/the-caves-of-portland/wellington-hole

A description of the cave, location and a load of photos.

Offline Colinstwenn

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Re: A new cave for Portland
« Reply #16 on: July 26, 2018, 10:03:32 am »
There is a tidal cave at Arromanches-les-Bains in Normandy.  It sinks at the foot of a small ridge behind Arromanches and resurges through cobles on a slip way in the beach.


At the sink there is a notice and a brief description of the cave.  It is only access via a pot on the ridge.  But no information is given of the location.

Offline martinb

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Re: A new cave for Portland
« Reply #17 on: July 26, 2018, 04:22:14 pm »
There is a tidal cave at Arromanches-les-Bains in Normandy.  It sinks at the foot of a small ridge behind Arromanches and resurges through cobles on a slip way in the beach.


At the sink there is a notice and a brief description of the cave.  It is only access via a pot on the ridge.  But no information is given of the location.

Ooo! Not far from me, here in Normandy. Anyone know of any other caves within resonable driving distance of Normandy?

Online paul

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Re: A new cave for Portland
« Reply #18 on: July 26, 2018, 06:20:16 pm »
Global Moderator Comment Probably not a topic for the "Portland" section of the Forum. :)
I'm not a complete idiot: some parts are missing!

Online tim.rose2

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Re: A new cave for Portland
« Reply #19 on: December 28, 2018, 09:31:29 pm »
Having been told the entrance to Welly was blocked a few weeks back myself and Richard finally managed to get down to the entrance today to take a look.  Seems the autumn storms have been messing with the cave.  The big lump of wood seen in the top photo in this thread (which we left to one side) had been washed about 10 m into the cave blocking the way on.  The sea had also kindly re-distributed a load of the rocks in the entrance area behind the lump of wood.

We've cleared the rocks sideways again and moved the lump of wood such that it can be passed and then wedged it with some rocks so with any luck it might stay there.  It's no surprise to us this has happened and I dare say will be a regular occurrence following a storm until we do something more permanent.  Portland hasn't received a proper battering this winter yet, only standard 40 to 50 mph winds so unfortunately I don't think this can be attributed to a single big storm. 

So for now, the cave is open.  We don't think any new rocks have been washed into the cave from outside, only those already in there had been moved around.  When the weather is better in the spring, we'll go back with a team and spend a few hours emptying the entrance area of rocks, dump them well out of the way outside and get the lump of tree out and deposit as above.   Hopefully that should prevent a re-occurrence for a while at least.

For now though, please bare in mind you might need to spend an hour moving rocks to get through the first 10m of cave (probably worth having a crowbar with you to avoid disappointment). 

Offline mrodoc

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Re: A new cave for Portland
« Reply #20 on: December 28, 2018, 10:55:19 pm »
I remember that tree trunk. We had to shift when we went in.

Online tim.rose2

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Re: A new cave for Portland
« Reply #21 on: December 29, 2018, 10:49:15 am »
The whole entrance area is certainly mobile and more importantly the wandering welly of wellington hole was found quite a way from where I last saw it.  We should start a game of 'where's welly?'.
There was quite a lot of seaweed in there as well - that should give the cave a fine aroma in the months ahead.

Online tim.rose2

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Re: A new cave for Portland
« Reply #22 on: June 04, 2019, 10:43:51 pm »
Myself and Richard popped down to Wellington entrance on Sunday to see how things are.  Once again the tree had been mobile and had more or less blocked the way on.  Less of an issue to deal with than the previous time though.
As far as we could tell new rocks were not getting washed in and it's simply those already in there being moved around by the sea.  We spent a couple of hours of evicting loads of rocks and dumping in places outside where they shouldn't get back in.  Having moved enough rocks to give a clear path we finished by rolling out the lump of tree that has been annoying and deposited it in the back of it's very own rock shelter 50 yards further down the cliff.  Hopefully it'll be happy there and not return!  We've left the last couple of large boulders which require clambering over before accessing the rest of the cave partly because we couldn't be arsed to deal with them and secondly as they seemed to create a good seaweed barrier.

We believe we've done enough to ensure there will be an open route through the entrance area for a few years at least and it's much friendlier on the knees than it used to be.  I guess time will tell.  If we're bored sometime we might well go and chuck out another batch.

The lump of tree and some of the boulders outside the entrance on route to their new homes...


Richard joyous at the now spacious entrance passage...

 

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