I'm not trying to minimize what happened in Centralia. It does seem completely crazy.
Dirt can absorb a LOT of heat. If you had to put out a fire, and you didn't have any water, you'd throw some dirt on it, right? We are all standing on a big ball of fire, anyway.
Having worked next door to the Sears Tower for several years, I can tell you that's a lot of dirt, distributed over the entire area of the fires. The only thing that surprises me is that it took so long for the effects to be recognized.
By comparison the carcinogens in Times Beach were on the surface and therefore easily measurable.