Exploration of the Excalibur MEGA extensions

We had an awesome night down Excalibur on 13^th August, probably one of the most exciting nights of new exploration since the 2020 Covid Extensions in Jenga Pot.

Last week set the scene (see earlier blog), with Dylan Kocher and Chris Curry having pushed an extremely tight and wet tube just off the upstream termination of the Excalibur streamway – a tube that had previously been either written off as too small, too unexciting or perhaps because reaching it in more average water levels if more of an ordeal.

Chris and Dylan reported around 40m of new passage including some high avens, chambers and crawling streamway, punctuated by a few concerning squeezes, ending at a fork in the streamway with open crawling passage remaining unexplored upstream. The plan this week was to enlarge the squeezes to allow more nourished or mature cavers to get through. We would then explore onwards, this time with me coming along for the ride rather than waiting enviously while the thin youths have all the fun.

Chris was away this week, but was replaced by Conor Morrison, so Dylan, Conor and I headed quickly down Excalibur at 5:30pm to get away from the hottest day of the year. Sparky and Malcolm were already down there, working to perform some long overdue enlargement of the entrance pitch-head. Andy, Gary, Max and Nial were to follow with alternative projects including Sparky’s dig near Oxbow Hall.

The stage was set for a productive night, and it did not disappoint!

We were quickly upstream and at the start of the new MEGA extensions, armed with a hammer and wide chisel. Dylan headed along the newly explored tube, followed by Conor, to commence work bashing of a few cherty projections, and to dig the floor of the second (tighter) squeeze that immediately followed. They may be skinnier and more hardcore than me, but I know a thing or two about improving squeezes. By digging the floor down from the streamway side, I was able to drain most of the water from the tube and remove several cobbles jammed in the mud, making the route ahead much more pleasant. Meanwhile, Dylan was doing an awesome job of scraping out the shingle floor beneath the second squeeze, with Conor unceremoniously sandwiched in between.

Dylan declared that we were good-to-go, and so he and Conor disappeared ahead, leaving me to commence my entry to the MEGA extensions along the tube. With most of the water removed, this was no longer an intimidating wet thrash, meaning I could take my time and move more cobbles aside. This barely classifies as a squeeze now, just a slightly awkward thrutch for 4m, to reach an enlargement in a north-south rift.

On the left (south) the rift continues at higher level but only for a few metres. The way on is right (north) immediately into the second squeeze which is along the floor of the passage. Dylan had expertly dredged this of shingle, and had progressed on to do the same wonders at the third squeeze, only 4-5m beyond.

Dylan had clearly aspired to make the squeeze passable, however, I aspired to make it no longer a squeeze whatsoever. With time to spare, I cleared the second squeeze further by excavating cobbles from the floor either side and dredging more shingle and pebbles from it, using a Hungry-Hippo style motion of grab an armful and wriggle back. After only five minutes, it was a simple 1.5m sideways wriggle, although it is now a shallow U-bend which pools water, so this delivered the first proper wetting of the day (very refreshing).

The second squeeze emerged into a much more spacious continuation of the main rift, about 1m wide and standing height... you could even walk for a few metres! However, only 4m ahead Dylan was just finishing work on the third squeeze, where the rift closes and the way on is a flat-out crawl over shingle and cobbles again. Dylan made an excellent job at dredging the floor again, and I finished the job off with some cobble removal as I slowly progressed through. This flat-out crawl extends straight ahead for 2m and then bends around to the right for 2m to rejoin the streamway.

Downstream, the way on quickly became too low, and is certainly the other side of the too-low section reached during original exploration 17 years ago. Above us at this point was an awkward squirm up through boulders into an overhead rift/passage, which averages 1-1.5m high and the same wide, leading off in two directions. Right for 3m reached a climb down, which a small amount of rock removal connected into the third squeeze at the bend. Left terminated after about 8m with the sound of the stream immediately underneath, but with no sight of the water. Just off from this passage are two sizable avens going up about 6-7m to very clean washed gravity-defying jammed blocks, but with no way on. This chamber is therefore a dead end but is very reminiscent of Fossil Chamber, which it must be close to; Perhaps the survey will identify a close connection that can be engineered.

Back at the stream, upstream continued in excellent crawling passage, with chert shelves and protrusions and large stream cobbles, but generally easy progress and with a great passage profile – very atmospheric. This continued for probably about 10-15m before turning slightly left and quickly becoming far too low.

Just before this, on the left (west) of the stream, a too-tight bedding was noted by Dylan, which produces an extremely enticing strong draught. A few small plan shoots emerged from the shingle floor searching aimlessly for light. This would be worth digging and should be easy progress to dredge the shingle floor.

On the right of where the stream starts to become too low, a route up through boulders conveniently reached another higher-level rift, which was very spacious indeed, 1.5m wide and 6-7m tall, and clean washed with razor sharp fossils. In the downstream direction the rift terminated, but a way on in the upstream direction could be seen 4m up, requiring a slightly exposed climb onto a balcony. Here, with exploration fever starting to take hold, I felt the need to remind my companions to take their time and don’t trust the quality of Jurassic limestone, as I suddenly realised how serious an accident here would be!

We carefully climbed up 4m in the rift, and then only 2m on, climbed back down to regain the stream, only a few metres upstream from where it is lost into the too-low section. We had therefore nicely bypassed the too-low section of the stream.

Upstream again continued in good proportion – easy crawling in an atmospheric streamway. Whiffs of organic matter, signs of surface debris jammed up near the roof and ominous dried scum provided a reminder that this is not the place to be in high water or if rain is threatened, and probably not in cold weather. Today however the water levels were low, it was the hottest day of the year, and with the water having only been underground for a few minutes at this point, it was slightly warm. This was simply delightful caving, and I was in total awe at these new extensions. I couldn’t stop smiling.

About 15-20m upstream brought us to the fork, where Chris and Dylan had turned around last week… Curry Junction. Here, two stream inlets enter, both appearing to be navigable into the distance, although notably smaller than the comfortable crawling we had been enjoying.

We took the left branch first, and I let Dylan lead the way. This continued as crawling, becoming increasingly awkward and gnarly, with some deeper pools requiring a belly dunking, which was great fun. However, after 15m we passed a slight right and then left turn when the passage started to become less fun and much more awkward. Dylan beckoned us on saying there was a small enlargement, which there was. Beyond there however things looked nasty, and it was clear that the end was soon to be found. Dylan pushed on another 4-5m but then reached a point where the water was entering from two tubes, both un-navigable without some serious work. We must be so close to the sinks that it would be unrealistic to expect much more upstream passage past this point.

Dylan returned feet-first while Conor and I effected a turnaround in the ‘enlargement’ (which involved some interesting body-origami). Conor returned to Curry Junction, but I noted a side-passage heading up on the true left (east) into a small rift with space to stand up. This was only 3m long and didn’t offer any continuation, but a slope down on the other side returned to a stream, presumably the other branch of the fork. Conor pushed up that branch to confirm the connection, and Dylan and then I followed. This branch continues for maybe 10m, but then Conor declared it was too tight ahead, which Dylan also confirmed. Game over!

Back at the fork, I spotted a rise into a rift, which I squeezed up into. Ahead, in a downstream direction, this continued for 5m to an unusual pile of 1 ft diameter stream cobbles, the kind you get on a surface riverbed, almost as if this was some kind of surface collapse at one point. Possibly Corner Sink? Or could we even have made it as far as being underneath the Big Sandy Sink? On the left was a loop passage dropping back down into the stream, confusing Dylan and Conor when I appeared behind them.

It was now 8pm, and we had explored all openly navigable passage, so time to start the outward journey, poking a variety of other nooks and crannies on the way out that had not been examined fully last week. This area is fascinating; A mixture of crawling streamway, punctuated with rises into more spacious rifts and avens. It has a great ambience, a very remote feeling, and is enjoyable caving, albeit a little physical at times.

Out of the MEGA extensions, the journey downstream reminded me of what an awesome streamway Excalibur Pot has, with cascades, chambers, stomping progress and excellent formations. This is easy to forget or take for granted. We smelt the black powder around Sparky’s dig, but they were long gone, however, we caught them at the newly enlarged entrance pitch, exiting at 9pm and in the pub only 15 minutes later to celebrate.

In total, I’d estimate the MEGA extensions to total around 100-120m of new cave (including all the side-branches), and this provides an awesome expansion to the classic upstream sporting trip for anyone wanting a little more adventure in low water.

There are a few high-potential digs, and the survey is now needed to see how close to the Big Sandy Sink we have travelled.

While we were exploring new cave and pushing the forefronts of UK exploration, Sparky continued to push his dig just 100m downstream from us, during which Andy accidently shat himself while adopting an awkward angle, and then suffered light failure. The North York Moors Caving Club strikes again… I chose my team wisely tonight!