Stephanie Wrote:
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> Spontaneous combustion, I don't think, would
> explain the 300 degree ground temp though, would
> it?
>
> Stephanie

Quite easily, I think.

There are places in the U.S. where underground coal fires have smoldered for decades, maybe even longer (it isn't always known when they started). Sometimes the cause is known to have been campfires or lightning strikes, but I wouldn't rule out spontaneous combustion in rare cases. Organic material (like half carbonized lignite) generates heat as it oxidizes, so a hot dry day & sudden exposure to oxygen (or wind to increase oxy flow) might well do it.

And once you have a SLOW underground fire (limited by oxygen ingress through the soil, or through the burned channels), heat builds up and slowly difuses through the regular rock & soil.

Paper burns at 451 F, I'd assume that lignite wouldn't be much lower. So a soil temp of 300 F nearby on the soil surface is entirely in line with expectations.

Kenuchelover.