Knock Fell Caverns trip 10/06/2023

Navigation

This was my first trip to this extensive cave. It is 4.5 km long, and has a maze cave structure so perfect that the survey looks more like graph paper than an actual cave, stretching just 342 metres in length and 130 metres wide, all formed on one major level, with a few passages dropping a couple of metres into a level below it. The round trip which this gallery covers is significantly less than 1 km in length, but we probably stretched it to over 1 km given our detours and additions, taking 3 hours for the whole trip.

The mind blowing thing is that the surface is absolutely peppered with shakeholes for the entire range of mountains, all following a contour ring for 8 km along the mountains, with another line of them 110 metres lower down going much further along the mountains. There are abandoned resurgences 400 metres lower down the same mountain (though separated by several non-cave bearing layers, including an igneous intrusion sill 200 metres down the mountain). The cave sits to one side of the upper line of shakeholes, with its entrance in one of them. This shows that the potential for more cave here is immense, and this is not the entire cave. It is just the fragment that has been found so far, and there are hundreds or thousands of kilometres of this cave system, just waiting to be found, on several major development levels.

In spite of sitting just below the surface, and having numerous points to take in water, the cave is completely fossil, so there must be lower levels draining it. It was formed as a phreatic maze, but there is no current catchment big enough to supply it, and it formed when there was more mountain surrounding it, a number of ice ages ago. The development was as a hypogenic cave, as part of the local groundwater, rather than an active river. This can be seen by the complete lack of scallops. The cave is in what must be some of the highest limestone in Britain, with a thick band of high quality limestone as high as 770 metres, just 75 metres to the south of the caves southernmost point. Thin limestone layers can be found interbedded with sandstones as high as 890 metres on nearby Cross Fell, but the thicker limestone beds are actually lower than 770 metres on that mountain. The cave entrance is at 762 metres altitude, with its shakehole passing through the thinly bedded layers into the solid limestone.

Beneath the high quality limestone are layers of limestones and shales, which dip down in all directions, and can be followed without interruptions to as low as 300 metres to the east, and potentially down to 150 metres a lot further away. The depth potential would be insane, but it is unlikely that good caves will have formed in those layers. That also makes it unlikely that the cave could connect to the lower line of shakeholes, and those would relate to a different cave system. The cave's limestone bed extends down to about 730 metres altitude, or 720 metres at its lowest point. The same layer reaches as low as 670 metres on the northeastern side of Cross Fell, but the cave would be unlikely to pass through extensive faulting on Great Dun Fell, so Great Dun Fell and Cross Fell would have to have their own system. The lower ring of shakeholes is formed by another layer of good limestone sitting below a sandstone layer, and there are a few other layers like it in the area.

Unless otherwise stated, camera, setups, lighting, edits and gallery effects by Tarquin. Modelling and lighting at various points will be Dinny Davies and Gwenllian Tawy.