Rottenstone Avens, named the Minuteman Silo by the original explorers, are a pair of immense interconnected avens, that are passed through on the route to the Rising. These were originally climbed in 1970 to reach what was intriguingly referred to as a "floorless chamber". Recently these avens have been reclimbed by Richard Frost in his quest to explore the higher level leads in DYO. At the top of the avens, the "floorless chamber" has a fantastic flat roof that is covered with a multitude of straws and stalactites, that Richard wanted to be photographed. The plan was to climb the avens, photograph the roof and then go and look for a "strange area" that was reported by Dave Judson and Glyn Edwards after their visit in August 1970 to contain a vast array of impressive helictites, blue and green tinted aragonite and gypsum formations.
At the top of the pitches a loose mud and boulder slope rises up to the fantastically decorated roof. At the top of the slope you have a commanding view of this "floorless chamber". We stood motionless at the top as the party climbed the aven one by one, to ensure that no rocks were sent hurtling down the 30m aven to the cavers below. Once all up, I tried to take a photograph of the roof. The camera refused to play and no matter what I did to it or what mode it was set in, even removing the battery and memory card would not shake it into life, so the photography was knocked on the head. An old hawser rope installed by Judson and Edwards dropped down the mud and rock slope to a narrow mud and boulder bridge that led to a larger ascending slope on the opposite side of the chamber. A belay was set up and Richard was lifelined across the top of this abyss, where at the other side he placed an anchor so a good rope could be installed to protect the crossing. At the other side the slope rose another 30 feet above the level of the roof to lead to an area where two alcoves containing the magnificent formations were located. Gareth and Keith followed to join Richard in the exploration of this part of the chamber. An array of formations unlike those seen anywhere else in Dan Yr Ogof were found, but no sight of the blue and green tinted formations mentioned in the 1970 report could be located.
Present: Keith Edwards, Brendan Marris, Richard and Gareth