Nugget digs a hole

Ok, so the title is a little deceiving.  Nugget just found a hole that was only superficially covered and dug in it :)  We have this "dent" in our yard where a tree used to be a long time ago.  Anytime I have dirt left over from any project I'm working on, I dump it in the "dent" to eventually fill it in.

The other day, I was working in the yard and look over to see Nugget dig, dig, digging away.  I go over to investigate and I find this hole at the side of the "dent."  My best guess is that it is a hole where a root used to be or another animal dug it.  I stuck a stick in there and it went down and then over about 2 feet!  Pretty long hole!

Enjoy the video of my super smart and talented dog!