I also see the triangle, on a steep slope with snow/ice patches.
Looks like an relatively open area, with evidence of having been burned over, so I suspect a natural feature. Standing and fallen tree trunks typical of a hot fire episode, so could be three trunks, all about the same length, that simply came together on the slope that way. I've gone out to investigate a lot of interesting geometrical shapes myself over the years, with about 90% or more being nothing more than a good excuse for a bit of exercise. But you learn a bit from every one I guess.