If a Tree Falls...?

I like puzzles -- even when it's impossible to know the right answer.

This hollowed tree trunk is obviously charred on the inside. Was the core already rotted away before the fire? Was the fire caused by a lightning strike or started by humans? If the latter, why? It's not likely to have been an attempt to make a canoe. First rule of canoe-building -- start construction close to water. This log is about a mile from, and a few hundred feet higher than Lake Padden.

Disclaimer:
To improve the blip, I removed a (smaller) rotten log. You can tell where it had been by the absence of moss and the shreds of rotten wood.