Cavechat.org

A question came up at my last grotto meeting that no one had an answer to. Every once in a while coal catches fire underground. There's been one burning under Centralia, PA, for the past couple decades. The recent movie Silent Hill involved a similar underground coal fire (only vapors from the coal wafted up and killed half the town).

Once a coal fire burns out, will there be a cave? Any passages people would be able to explore?

Sean Ryan wrote:Once a coal fire burns out, will there be a cave? Any passages people would be able to explore?

There will be a mine, which is where these fires (always?) start. After the coal burns away, the mine will probably be even less stable than it was before the fire. Sounds like a good hole to stay out of.

No cave is left...

Or at least nothing that is big enough for someone to get into.

The overburden can go down, the underlying clays up, and there is ash often left over from the coal burning.

A seam without a mine can burn, as long as the oxygen can get through.

They're a real problem to get extinguished.

About the only thing that would be left is a highly unstable roof that CAN and WILL collapse and NO oxygen to breath!!!!!!!
If you want to commit suicide this would be a place to succeed!!!!!!!!
Best advice is STAY OUT!!!!!!!!!!!

Don't worry; this is just hypothetical. Besides, the only place I know of this happening is Centralia, and there's no signs that puppy's getting extinguished any time soon.

Sean Ryan wrote:A question came up at my last grotto meeting that no one had an answer to. Every once in a while coal catches fire underground. There's been one burning under Centralia, PA, for the past couple decades. The recent movie Silent Hill involved a similar underground coal fire (only vapors from the coal wafted up and killed half the town).

Once a coal fire burns out, will there be a cave? Any passages people would be able to explore?

Interesting thought - is this an overlooked avenue for non-limestone speleogenesis? Consider the scenario of a deep coal seam under some relatively stable overburden. Seam catches fire somehow (mine accident, lightning strike, lava intrusion, whatever) and burns for a long time. Eventually, the fires go out and what had been a coal seam is now filled with ash, clays, etc. Add water to flush out the residuals and, viola, cave!

If ya think about it, it's amazing that we can launch rockets into space, but can't put out an underground coal fire. Would it not be possible to flood the mines or something?

Most coal forms in really rotten rock. Occasionally not, but shales and clays and thin nearshore limestones don't make good caves. I cannot speak to the metamorphosed Pennsylvania strata, but if mines weren't in unstable rock, they wouldn't need the shoring they do--as compared to underground limestone mines or hardrock mines.