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I have heard that a fire in a cave or under an overhang can cause a rock collapse, potentially injuring the occupant. Is this a real risk?

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5 Answers 5

up vote 5 down vote accepted

Is this a real risk?

Yes.

However, I would have thought it's a much higher risk with soft rock, such as sandstone, which could easily crack and break apart due to heat. I'd imagine the risk would be lower with something like granite, but I'm still not sure I'd risk it unless the cave was very large and well ventilated.

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It is also a high risk in low temperatures where thawing due to the heat can let water get deeper into rocks where it may freeze again, emerging cracks. Still not a huge risk but I wouldn't do it myself- fire just at the entrance works best. –  Rory Alsop Oct 3 '12 at 7:14

The only time I lit a fire in a cave we had to evacuate due to smoke and a billion spiders dropping from the ceiling.

Much better to light it just outside :-)

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This an anecdotal comment and not an answer to the question. –  DudeOnRock Dec 26 '12 at 4:36

The general rule is that the rock can't get hot. When you heat the rock, the water inside evaporates and can crack the rock. If you're just making fire to warm yourself or cook something (a steak, not the whole beef) it will be OK. When the fire is moderate, the rock shouldn't even get warm.

You shouldn't also throw bigger stones into fire. They can explode.

The example cited by berry120 was something like the-biggest-fire-in-the-world-challenge... When you want to fire something big in the cave, I would be afraid of CO intoxication in the first line, however.

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There is another problem with making a fire in a natural cave: the smoke propagating through the cave can severely affect various cave-dwelling species, particularly bats. That is especially bad during winter, when smoke and warm air from the fire can wake up the bats and drive them out of the cave, causing them to freeze or starve to death.

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Thank you for sharing this. It is an excellent point, often overlooked. –  Russell Steen Oct 29 '12 at 15:18

At first, I was going to down-vote the question, because "I have heard..." struck me as relying on urban myth. But I realized I didn't have the Rep yet on this site to do so...

Then coincidentally, I came across this sad story from 2009:

A 16-year-old boy was crushed to death by falling stones in a cave which had probably been unsettled by the heat from his camp fire, an inquest heard.

...

Geology expert Andrew Bowden told the inquest that a pre-exisiting weakness in part of the 1,000-year-old cave would have combined with the heat of the fire to cause about 200kg of rock to fall away from an overhang.

[Edit: This refers to the same story linked by Berry above]

But under normal circumstances, I suspect Carbon Monoxide poisoning and/or smoke inhalation is the bigger risk...

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ASKING a question about urban myth, rumor, or pure speculation is perfectly legit, and should not earn a down-vote. ANSWERING a question based on urban myth, rumor, or pure speculation is bad, and should be down-voted into oblivion. –  LBell Oct 22 '12 at 13:12
    
Fair point... but is providing a link to a prominent news site (the BBC) "answering based on urban myth"? –  Andrew Oct 23 '12 at 6:27
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Nope, it is not. I did not mean to imply anything about your answer in particular, just giving some general thoughts. (I did not down-vote your answer.) –  LBell Oct 24 '12 at 17:10

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