Cave collapse risk

[phillip1]

This may be a stupid question, I have always wondered about the true potential risk of a partial cave collapse. I know that water pressure plays a crucial role in ceilling support but what about in very shallow breakdown type caves were there would be minimal pressure.
I was diving a sump here the other day and it's a really cool access pool in a huge dry cave, the entrance is shallow like 2-3 mtrs tops and it is very tight for the first 10-15 mtrs then it opens up into a big room, it is limestone but kind of frail and soft type & like many breadown type caves it looks like it is going to collapse, although I am reasonably sure (& hope) it won't.
There have been incidents were dry caves have had collapses, even here in Cueva Voodoo a big rock the size of a small car fell and almost crushed a tourist here a few months ago, but I have never heard of a wet cave collapse.

[stairman]

Sure the risk is there.Ive never seen a colapse or the siltout caused by one and hope I dont.Its strange that the Peanut tunnel is strewn with boulders that have obviously fallen and the Pothole tunnel is primarily mud.Is that ceiling more stable or is it just younger and hasent went through process of breakdown? Either way I love the contrast of two very different caves at one place,and i figure they have been there thousands of years so Ill take my chances as does everyone else.

[rjack]

Choc Mol in Puerto Aventuras Mexico had a collapse in the cavern area last year. It was a pretty large piece of ceiling, the size of a couple buses. Its a popular cavern tour location, not such a great cave dive. Fortunately, the collapse happened at night so no one was injured or killed. Other areas in Chac Mol and other systems have stalagtites that are 10,000+ yrs old so obviously those ceilings have been pretty stable. Who knows what will happen tomorrow.

[skip]

I've read that water pressure/density is partly responsible for holding up the ceiling. If the water level drops enough that the water no longer supports the ceiling collapses may occur.

A cave here in TN has a big triangular rock in the middle of wide passage. It was not there for years and then it was there and is now. A recent dive was clear enough viz I could see the ceiling where it fell from, where it fit like a puzzle piece and worried that another chunk might fall as I looked, so hurried on.

-skip

[Sludge]

I was diving JB several years ago. I went to p2,500' and turned around. The vis had been 100'+ on the way in. Went I got back to p700' the vis went to crap until I got to p400' and outran it (I was scootering). In the cavern I passed a team of three divers who were exiting.

At the surface I asked them what had happened at p700'. They said they had done the Horseshoe Circuit and had only penetrated to p500'.

We were the only people there that day.

[phillip1]

There are some really freaky looking dry caves here that you have to climb down to get to the sumps here, and by freaky I mean the entire cave looks like it's held in place by a few marble sized rocks, with house sized boulders just waiting for an excuse to fall. Always makes for a very interesting diving experience.

[Webmaster]

A cave is by definition a weathering feature (and no, I don't count breakdown caves as accretionary), it will ultimately be destroyed by the same forces that form it. Breakdown modification is part of that, rocks will fall. Whether you happen to be there to see it is purely coincidental.

Above or below water, it's going on all the time. I've seen rocks fall on their own before and it's a very odd feeling. I've also seen rocks that looked as though you could breathe on it hard and it would fall, but we couldn't get it to move after jumping up and down on it.

A lot of times it's hard to tell for sure just how unstable an area may be without trying to instigate a collapse. I would say use your best judgement, and if it looks precarious either clean it or don't touch it.

Marbry

[MengTze]

.....the Peanut tunnel is strewn with boulders that have obviously fallen ...

We saw one of those fall in 2005 while swimming through there, right next to me, scared the F out of me......

Beyond that never seen one fall or a collapse anywhere.

[Guy Bryant]

During 1980 I explored and mapped Pot Springs on the Withlacoochee River in Florida. Most of the cave is small but there are some areas with tunnel big enough to accommodate two divers side by side. Anyway, there is one area that had a large boulder blocking the passage. So, in 1987, Court Smith, Lamar English and I set about widening it. We eventually got enough of the boulder chipped off to squeeze past with side-mounts.

After this episode I dived once at Pot Springs in 1992 and again in 2000. On the 1992 dive I was surprised to see that the boulder had slid and totally blocked the passage. Man, I would have not wanted to be on the wrong side of that boulder.

In 2000, I noticed in the main tunnel (which had been large enough for two side by side divers) a huge slab had fallen from the ceiling and totally covered my line for about 10 feet. It is now a single file squeeze over the huge slab to continue onward.

I've never seen a boulder fall or ceiling collapse but I've sure seen the after effects to know that it can and does occur. Hopefully, one won't be around when it does occur. If an area doesn't look stable then I would err on the safe side .... don't touch it .... step away from the cave.

[Randy Thornton]

Boy, you fellas really know how to make a guy sleep well at night!