I was out walking the dog this morning and came across these two 'caves'. They are natural and big enough to get completely inside. They are formed in the Penant Sandstone of the South Wales Valleys. But can they be classified as caves?


The caves' setting.


'Rift Cave' entrance


Inside 'Rift Cave'. The rift is about 0.7m wide and goes back about 4m. It's about 3m high at the entrance but with the floor rising rapidly, is crawl at the back. A through trip would be possible but some loose rock would have to be moved. The upper entrance is a flat out crawl under a huge slab of bedrock but I didn't take a photo of it.


Detail of the main roof of fallen rocks. The roof isn't solid but I remember reading about caves in a granite canyon in the US, where fallen boulders and earth formed the roof.



Entrance to other 'cave'.


Close-up of entrance.


Chamber inside cave. It's about 3m wide, about 2m front to back and about 1m high. At the back is an open rift which is letting in the daylight. Again a through trip would be possible but tight, you would exit off to the left. The whole thing is a void in solid bedrock.


The right-hand side of the chamber.


So the question is, are these things caves?

Yes. Small ones.

Without being able to see too much in your photos, I would say that they are probably caves

Similar examples can be found in the Fell Sandstone of Northumberland & I have written a number of papers about them.

See especially:

Mullan,G.J., 1989. Caves in the Fell Sandstone of Northumberland. UBSS Proceedings, 18(3) , pp 430-437

and

Self C.A. & Mullan G.J. 1996, Redefining the boundary between karst and pseudokarst. Cave & Karst Science. Vol 23 (2) pp 63-70

I think young children are often the best judge of what something is. Ask a five year old. Adults tend to complicate things by trying to be clever.

I reckon they are caves, but probably not Karst...
A cave is defined as a void large enough for a person to enter and it seems they tick that box so...

They look very similar to things in the peak district that have been given names - such as robin hoods cave etc on the gritstone edges of the peak district. IMHO, yes, they are caves.

There is a section in COPD (Peak District) on "Gritstone Caves", not in limestone but still underground.
IIRC there was a discussion about this many, many years ago WRT "Threshold of daylight" defines a cave (or not ?)

I don't think they're not caves  :blink:

The one with the chamber inside looks like the entrance has been enlarged a bit.
Looks like a damn good bivvy spot. 

Mike Wood said:

I don't think they're not caves  :blink:

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Do you think they are caves?

Well, it doesn't look like it's a mine, it looks natural, and it's more than ten foot long.

Les W said:

I reckon they are caves, but probably not Karst...

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Les, read the paper in C&KS that I cited by me & Charlie.

Interesting. My first impression on seeing the photos was tectonic caves but 'close up of entrance' got me thinking pseudokarst.

I think they may have been formed in different ways. The first cave is probably a techtonic rift that has become roofed over with rock, earth and grass. The second one could be solutional, with a techtonic rift at the back. I really don't know what I'm talking about of course!

The consensus seems to be that they are caves so I'm happy. I'll get my 8 year old to think up names for them. I suppose I should get accurate grid references and survey them - shouldn't take too long!

Pennant Sandstone is very similar to Millstone Grit.  Caves are quite common in both rocks and are generally formed along beddings and faults where sandstones become friable and can be eroded by wind and/or water in exposed locations.  Most are no longer than a few feet but there are lengthier ones in gritstones in the North.

I once asked this question in respect of some sea caves and was told use the drip line test (that is, does the roof go up so as to form a point from which a drip can form).  The trouble with daylight threshold (assuming you are looking in the day time) is that you can get a long way in some places and still 'not' be in a cave (like standing on the floor of the main chamber in Gaping Gill).  But there again you may not get a drip line on some entrances.  Is there an accepted group of tests to determine if a concavity is a cave?  (A serious question in the light of other threads on 'Open Caves'.)  Afterthought - I presume we do agree that we are dealing with concavities and not convex bulges.

Please can I have an NGR?

I can get you a rough grid ref off the map Tony but best to wait until I get a chance to get back with a GPS. It's only a half hour walk from home so shouldn't be too long. Do you want the info for one of your guide books or do you think the caves may already be recorded?

Huge said:

I can get you a rough grid ref off the map Tony but best to wait until I get a chance to get back with a GPS. It's only a half hour walk from home so shouldn't be too long. Do you want the info for one of your guide books or do you think the caves may already be recorded?

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Both  :spank:

Define a cave?
Look like caves to me but without being there I cant judge clearly.

They look ideal places for a caveman to sleep, light a fire, raise a family and cook Sabre Toothed Tigers. That makes them caves... (Peter's right)