A thing difficult to explain

One of the many things I like about riding with Ken is that he tends to look around while he rides.  A lot of people who ride mountain bikes just ride, always looking at the trail in front of them.  And I think that's okay.  But it's also nice to have a look around now and then, too.  Stop and smell the flowers.  Stuff like that.

Some time ago, while we were out riding together, Ken pointed out a curiosity to me alongside a trail folks around here have always called The Onceler (now officially a part of the Arizona Trail).  Just for fun, I stopped to have a closer look at it on my morning ride today. It's little more than an old stump and a couple boulders at first glance.  But look a little closer and it becomes difficult to explain this feature.  How did those two large boulders end up on top of that big old stump?


Best I can come up with, short of, "Someone put them there, duh!" which seems unlikely, is that they long ago rolled down the hill together and got wedged into the old stump by chance.  But even that explanation seems unlikely, as they would have had to both sorta jump up onto the stump together in order to get wedged in there as a pair.  The mystery-feature is in a steep-sided, minor drainage.  So, I suppose it's possible that at some point there was some kind of major stream flow that raged down it long, long ago. Possible but, again, not very likely, as there are really no other signs of such a catastrophe in the area.  At this point in history, the drainage appears quite minor, carrying a bit of snow-melt runoff in season, but that's about it.

Not the greatest mystery in the world.  But a fun one to ponder.  Frankly, I'm stymied.  I really can't explain it.  At all.

Got a good guess?  Do share.