On the subject of exploding matter. Be aware of placing eggs in hot embers: they can and do go with quite a bang! Although they are placed in a different category of danger I suppose...

Like Chris Kavanaugh said, fire travels UNDER GROUND in roots.

I put out 'smoldering' ground that was 3ft away from the fire PIT. THe fire pit was 1ft tall, and was cleared 4ft to the nearest brush...

The fire was ALMOST to the brush when we put it out, we had to dig down 1ft in the soft soil to put out the fire w/water. Luckily there was a stream about 50ft away so our trips with water bottles was much easier!

Be careful about fires!

Someone else mentioned exploding rocks a myth... It's not my mom has been hit by parts of an expoding rock. This was in a camp site when I was growing up the lake was a good mile away, and the rocks had been near the firepit when we arrived they were smooth and rounded like so they weren't 'earthy' looking.

Absolutely! Think of Centralia, Pa!

Centralia Pennsylvania Mine Fire

From what I understand about it, someone was burning some trash and mistakenly set an underground vein of coal on fire back in 1962 - and it's still burning!

Whoa. That's cool.