Hartley Nature Center says they're just taking advantage of the snow cover to safely burn a series of debris piles (and a little storm damage) left over from a logging operation this summer.
It's not an official park activity or anything, but the park is still open, and if you're out for a ski or a walk in the 20-below wind chills and you happen upon some folks tending a nice blazing fire ... and you happen to have some marshmallows in your pocket, well - so much the better.