Depth through thought
OUCC News 31st May 2006
Volume 16, Number 7
|DTT Volume 16 Index|
Editor: Peter Devlin: firstname.lastname@example.org
We are never short of space to squeeze in a little write-up of a caving trip, so please contribute to DTT.
Here are the trips planned for the remainder of Trinity Term:
Week 6, 2-4 June, Dales staying at BPF, permits: Hammer Pot and Mongo Gill, coordinator: Dave Legg
Week 8, 16-18 June, Wales staying at WSG, no permit, coordinator: TBD
Steve Roberts [club weekend OFD, 21/5/06]
To think that I'd been lying dozing in my pit between about 7 and 9, thinking how pleasant it was to hear the rain spattering on the skylights without any urgent necessity to get up. Chris had to catch a train in Bristol at 4pm; Fleur was his lift. Thus we were in the nearly unprecedented situation of getting underground before 11 on a Sunday.
The aim - to show Chris round OFD2, avoiding the streamway which given the hideous weather over the last few days would be suitable only for suicidal speed-canoeists. Thus Top Entrance - Salubrious - Selenite - Edward's Shortcut - Gnome and out was decided on. Fleur knew the way. I'd last done the route about ten years ago.
A swift, efficient but unrushed trip followed. The traverses in Edward's Shortcut look scary. They are of the "feet on one side, body across the gap, hands on the other side" variety, so the traverser cannot avoid a fine view of the beckoning darkness below, unless of course (s)he closes his eyes - most unwise. But in fact they aren't too bad, with big ledges, and plenty of grip. It helps if you get someone utterly confident (Fleur) to go first; I have always been a grade "A" wimp about traverses.
Selenite passage was as pretty as I remembered it. Chris was impressed: both with the cave, and with the pace set by Fleur, who was determined that he wouldn't miss his train. In fact, we were on the surface again at 12.30, despite a photo stop in the "Big chamber near the entrance", so we would have had time to go round it all again...
In celebration of my return to digging Tim has created a new digging group known as the "emeritus diggers". Actually to be fair I don't think either Ben Lovett or Chris Densham are truly "emeritus diggers", as they have both been digging very actively recently so whilst they may fulfil the old and experienced criteria, they probably don't fulfil the retired bit. However Tim and I have not been digging for about 18 months, and even then it wasn't very successful because I just wasn't quite ready; it has really been 6 years since my last proper digging trip.
As I travelled through Ogof Draenen to Life on Mars with Tim, Ben and Chris on Saturday I had strong déją vu. I was last there (with some combination of Tim, Ben, Lev Bishop and Pete Bolt) somewhere between 7 and 8 years ago, during what I have now come to think of as Life Before Pelvis, which seems a very long time ago. Nevertheless on Saturday we would come to a piece of passage where I would see a particular rock shape that suddenly seemed remarkably familiar; the cave is exactly the same as it always was, and it all felt rather strange. In fact I think that in Life on Mars the strange dissolution features, dry atmosphere and silence do give everyone a sensation of timelessness and of being somewhere very old and unchanged, perhaps like Mars?
I was quite keen on Life on Mars because I thought it was nearer and easier than Dollimore's or War of the Worlds and less scary than Wessex for my first day trip digging in Draenen since Before Pelvis. Despite this I did have a vague recollection that this was actually quite a difficult trip that I used to find almost as tiring as Dollimore's, and have trouble getting my dodgy knee through some rather awkward rifts. But I conveniently blocked out these memories and concentrated on the fact that it looked nearer on the survey! Also I was feeling quite confident after a very successful tourist trip to Dollimore's with Tim and Richard and Elisa a few months ago which was far easier and less painful than I had expected. There was also the added bonus that Ben was going to show us a new route to Life on Mars which meant that Tim, Chris and I would be going through passage in Draenen we had never seen before.
The entrance was rather damp after all the rain, but it didn't take long to reach the pitch down to Players Tunnel and we were soon into passage that was very much in need of conservation taping, so we spent a couple of hours taping a path through the nice mud and crystal formations. It was lovely to be in such untravelled territory - much of Draenen has a rather slippery trade route feel to it these days. The Life on Mars rifts were quite awkward - Tim almost got stuck in one finding his chest is slightly larger than it was 7 years ago. I found it quite awkward and needed quite a few extra footholds generously provided by Tim and Chris in the form of knees and shoulders.
It was a great place to dig with several options so nobody got cold or bored, and some nice digs which were just sediment that needed digging with a trowel. Everyone worked really hard for many hours and it was great fun shovelling mud and hauling boulders. There is still debate as to whether it is strategically a good place to dig or not, given that it could be a lot of digging to reach anything significant. However it was all very rewarding as progress was quick and everyone had several small breakthroughs. We made most progress (about 15 m) in one mud dig where we had two small breakthroughs into what can be termed new passage, albeit it rather small new passage. I particularly enjoyed squeezing through the tight bit into the new passage - just like the old days, even though I just found another dig round the corner - just like the old days. There was some hilarity on the next breakthrough when Tim excitedly announced the discovery of "a chamber". Chris followed and asked where the chamber was to be told that he was in it! "The turning chamber" was actually quite useful as it meant two people could pass and one could turn around and come back through the tight bit forwards rather than backwards. We carried on digging until it was almost too late to get out in time for the pub and certainly too late to drive over to the WSG. It had all been too much fun and I was pretty exhausted and slow on the way out, ticking off each landmark and trying not to think about how many more there were to go. Chris headed on to keep the pub open and then Ben did the same in the entrance series but he heroically took two heavy bags and then I had a new lease of life from water and sweets so we caught him up! Just like on the Dollimore's trip my pelvis was far better than I expected and I am looking forward to the next digging trip, but lots of thanks to the Tim, Ben and Chris for carrying my share of the bags a lot of the time and providing excellent footholds in all the right places.
During my recent trip to France to meet karst scientists at Rouen University who have been working on the Chalk karst for many years I was taken down two Chalk caves in Normandy. Chalk caves. Chalk is the stuff we write on blackboards with, the soft friable rock that forms the gentle rolling countryside of the English Downs, not your usual cave forming rock. However, Tim Atkinson (from UCL) and I were told to bring caving gear for the field visits, so I imagined that this must be because we were going to have to crawl down small short muddy tubes. It turned out to be a very surprising day........
We were told we didn't need to put on caving gear for the first cave which turned out to be one of the most amazing digging projects I have ever come across. The cave is a fossil system; it is now completely dry, there is not even any dripping from the roof. When the cave entrance was revealed by quarrying, the cave was almost completely sediment filled. The local digging community have excavated the sediment to create a walking sized 400m long cave. It is now between 2 and 5 m wide and 2 and 5 m high although the natural passage is in fact considerably deeper as the sediment on the floor is ~ 7m deep. Imagine how much work has gone into removing all the sediment even with the very efficient tram and pulley system they have in the cave. The diggers found some quite long sections where it was possible to crawl through open passage, but all this has been excavated to reveal the true and impressive dimensions of the cave. The diggers had one exciting breakthrough where they dug up into a short section of the main passage which was open walking sized passage.
The walls and roof are white Chalk with flint bands and frequent solution pockets, and the passages have an arched phreatic shape. It is thought the main passage may have formed upwards by paragenesis. This means that sediments filled much of the passage resulting in dissolution of the roof. The passage winds around corners and and varies in shape and size much as a limestone cave does, although it was not as complex as the maze like systems we are used to. There are three main side passages, all of which were totally sediment filled prior to digging. Two of these go steeply down from the main passage, perhaps joining to form an as yet undiscovered lower level. The chamber excavated to one of these is a very impressive size (in fact there was a long ladder that we were unable to descend on our visit). The third side passage goes up towards the surface, and is thought to be one of the original swallow holes that fed the cave system. Beyond this the main passage continues to the end where sediment is currently up to the roof level and the digging continues.
The second Chalk cave was even more surprising and for this trip we needed proper caving gear. The cave system is around 8 km long, although it is a bit dissected by the Chalk mines that have revealed the natural cave passages. The mines themselves are an impressive demonstration that in France at least, the Chalk is strong enough to support enormous cavities. I estimated the mine passages were up to 20 m wide. As you walk through the mine you come across natural cave passages (with entrances on both sides of the mine passage). It is obvious they are natural because they have classical rounded dissolutional shapes in contrast to the square cut mined passages. We entered several natural cave passages but didn't follow them for long. These had varied shapes and sizes, often with small straws and stalactites on the ceiling. Three of these have been dated and I think they varied between 40,000 and 130,000 years old, but I can't remember exactly. At one point we were taken to a spectacular natural shaft. Looking up I could not see the roof which was more than 50 m above. It looked like a (dry) Yorkshire pothole, or even something that wouldn't look out of place in the Picos. We finally reached our many objective - an active Chalk stream cave passage. This is I think about1 km long. The stream is very small but the passage is walking or stooping throughout. There are 26 large chambers at regular intervals along the passage. These were too big to photograph without flashguns. We didn't have time to follow the passage to the end (a sump), we went to about chamber 10 or 12, but I did have time to get my oversuit dirty squeezing through a muddy keyhole shaped side passage and dropping into a muddy chamber beyond. I climbed up a muddy greasy climb and then on up through a chamber. I came out in a large aven with a rope hanging down. On close inspection I could see some pitons in the wall where the local cavers had aid climbed up the Chalk. Tim Atkinson joined me, and we admired the rather spectacular aven speculating that the climbing project must have been quite challenging. Sadly it was 9 pm and time to leave having seen only a small part of a fascinating Chalk cave system. In France at least, caves in Chalk are well enough developed to provide some good local entertainment for cavers in Normandy and other Chalk regions.