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 Hang Tron (Circle Cave) 

Phong Nha System; Son Trach; Quang Binh
 
Deb Limbert, Robbie Burke, Ian ‘Watto’ Watson, Pete Whitaker, Mr. Diep, Peter
‘Snablet’ MacNab.
 
Located at the foot of the Hang Thung enclosed valley, the Hang Tron entrance was not the easiest of entrances to find. Our guide Mr. Phong disappeared off through a bamboo thicket leaving us perched amongst some pinnacle karst savoring a cool draft issuing from small fissures, a welcome relief
from the heat of the Laos winds (and a good sign from the cave somewhere below). Mr. Phong was scouting out the route to a cave he had visited ten years earlier whist collecting wood and animals from the forest. A whooping noise from below and to the right, Mr. Phong must have found the path. Our porter, Mr. Tintin, blazed the way. The whooping obviously translated as “turn right at the rattan vine and go over the gnarly boulder pile until you meet the obvious overgrown trail”. A glimpse through the forest of a white cliff face ahead hinted that we were close, as we rejoined Mr. Phong in a small clearing. Some delicate pinnacle and boulder hopping led to a sizable fossil entrance, it looked good, very good.
 
The usual formalities and preparation ensued, and we were shortly surveying our way down a boulder strewn borehole into the unknown. With excitement mounting we soon reached a chamber with a lake, or was it a river? Time for wetsuits? Not quite! Deb shouted back that she was in a dry fossil passage with a howling draught. A consensus was quickly reached that surveying in dry passage was easier than surveying whilst swimming. We scrambled up a mud slope into a very pleasant decorated passage, which rapidly revealed a large chamber. The source of the strong draught was soon discovered, as a further antechamber opened out into a daylight rift. We cracked open a flapjack and a packet of gummy bears, whilst discussing the merits of surveying with the expeditions new Disto laser measurer, (kindly sponsored by Leica instruments). With over 400m under our belt, we eagerly headed back to the main lead, with visions of river cave heading of into the distance, filling our heads. 

From the lake chamber we swam following the largest passage into a typical Quang Binh river passage, we were heading upstream. Pete checked out a dry inlet, and vanished for an eternity. We were just about to send out a search party, when Pete returned with a full and detailed report, “What have you  found Pete”– “A passage!”, “Does it go?” “Yes!”.  through some great passage. After negotiating a short fun section of rapids we continued up the main river through some great passage.

After negotiating a short fun section of rapids we arrived at a collapsed skylight, which cast spectacular sun beams across the next swim. Unfortunately this turned out to be the final swim that ended in a boulder pile with glimpses of daylight beyond. This was thought to be the other side of the boulders and tubes, which Jrat and Carl got into during their 1994 recce.

Backtracking, we checked out all the side passages and oxbows. We wrapped up the survey question marks, as we excitedly headed for the down  stream unexplored passage. Unfortunately, a 60m swim through a low arch, revealed that diving would be the only way to continue exploring the main downstream passage. We checked out the remaining stream passage which rapidly degenerated into low airspace ducks, these were soon abandoned and generously donated to the next generation.
 
We returned to Pete’s lead and surveyed our way along a very Dan-yr-Ogof (ish) passage, it even included the ‘Bakerloo Straight’. We remarked on the
similarity, and turned a corner, only to come face to face with the ‘Green canal’ (at Welsh temperatures). This is more concluding evidence to prove Martin
Holroyd’s hypothesis; ‘The cave in your thoughts will become the cave you discover’. We must remember not to talk about British caves when exploring in
Vietnam. Through the green canal the passage led to a boulder slope running in from the left, which brought us full circle back to our original entrance.
 
For the sake of completeness, we carried out a photographic record of the cave. The majority of this took place up the dry passage and big chamber, in
which we had stopped for gummy bears earlier that morning. Robbie organised the proceedings, as artistic director and photographer, using Watto as his muse. The rest of us operated the flashes. We were busy working through a catalogue of Leica disto sponsorship, spectacular formation, big chamber, and backlight passage shots, when the photo shoot came to an abrupt end. The photographer innocently remarked that the shot looked good! except for a certain part of the model’s anatomy being overly enhanced by the consumption of a popular alcoholic beverage. At which point the model in question exploded, the gist of which was, where the camera was going to be inserted if the last photograph was not deleted immediately. This reduced the rest of us into hysterics. When we eventually stopped rolling around the floor, the passage was consequentially named ‘Grumpy Bear passage’.
 
We had successfully put 1.2km of classic Quang Binh caving into the bag on our first jungle outing, and were pretty pleased with ourselves. The discovery
of Hang Tron completes another piece of the Phong Nha hydrological jigsaw. Hang Tron along with Nightmare Cave and Hang Tra An (with the exception of a few unexplored sumps) accounts for the main Phong Nha river from the Ho Chi Minh highway to the Hang Thung Valley. Although a large percentage of the Phong Nha river system has now been explored, there still remains the elusive link between Hang Thung and the Hang En valley. This will no doubt be a focus of future expeditions and involve some exciting caving and jungle experiences.
 

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