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Hallowe'en Rift, Mendip Hills

Excursions [and other notes] involved in the exploration of Hallowe'en Rift; a cave, so far, formed within Triassic Dolomitic Conglomerate.

The exploration of Hallowe'en Rift was started in 1982 by Trevor Hughes with other members of the Bristol Exploration Club, then during the early 1990's Vince Simmonds and other, mostly, local diggers were active at a number of locations within the cave, including the start of the dig to the 'east' side of the entrance, leading to An Unexpected Development in August 2018, with Graham Johnson in December 1991. The current phase of exploration was commenced in 2009, with the majority of the early work being carried out by Vince Simmonds and Alex Gee, now the regular team also includes Rob 'Tav' Taviner, Graham 'Jake' Johnson, Nick Hawkes, Jonathon Riley, Paul 'Brockers' Brock, Roz Simmonds, Duncan Price, Mike Moxon and Matt Tuck. There has been occasional help from others including Mike Willett, John 'Tangent' Williams, Pete Bolt, Bob Smith, Callum and Hazel Simmonds, and several appearances by that well-known antipodean, Ray Deasey.

There have been visits from some notable experts in their various fields including: Charlie Self, Andy Farrant, Christopher Smith, Derek Ford, Joyce Lundberg, Don MacFarlane, Marc Luetscher and Gina Moseley. All have added to a better understanding of Hallowe'en Rift.

24th August 2019

digging 2019 Posted on Sun, August 25, 2019 05:56:43

Vince, Nick, Jon, Brockers and Tav.

When we arrived at the cave entrance it was apparent that there had been an isolated collapse of the retaining wall. The most likely explanation is a slump of the material behind the wall as it became saturated in a recent deluge. However, anthropogenic interference cannot be ruled out either.

I was at the digging end of the Cold Gnarly North aided by Nick who was also, there was loose material remaining from the last session that needed bagging up. Jon was in the ‘lake chamber’, it didn’t appear to be any wetter than it was at the end of the last visit. Jon was digging too. The Lake Chamber Dewatering Project was underway, a low, small phreatic arch that Nick had noticed was exploited and there is a sandy silt layer that with a bit of work might allow the water to drain through. Brockers took up position at the intermediate corner and I suspect he found something to poke at in between loads. Tav was at the ‘junction’, at the end of the line, hauled the loaded skip and emptied the contents, the spoil was stacked in the entrance, so time was saved at the end of the session. Everyone was busy.

On arrival at the end of the Cold Gnarly North, Nick commented that there had been a change since his last trip up to the dig. The bedding has been expanded considerably and after this session is even roomier. The route up to the aven is relatively comfortable but there is scope for more improvement here. There is plenty of loose gravel and compacted fine sediment to be removed on the route to the aven. Access into the aven will need some attention but it appears ‘diggable’. Air movement is felt at the current end of the Cold Gnarly North but pinpointing its origins is not so easy. Nick and I discussed the origins of the fills and the potential ways forward, there are several options, all require the removal of a considerable quantity of sediments. There is a low arch to the east side of the aven that might be a possibility.

Time had passed quickly, and we left the Cold Gnarly North to move todays stack of filled bags and rocks out to the surface. 45 bags and 16 loads of rock were added to the spoil heap. A fine effort.

17th August 2019

digging 2019 Posted on Sun, August 25, 2019 05:54:59

I was away digging on Gower with Jon, others had their own commitments, consequently there was no activity at Hallowe’en Rift.