Dave25
ArboristSite Operative
Oh OK yes I have heard of that happening too. I think what you might be seeing is a part where a branch broke off. It has had two bigger branch break off, I believe in storms but I'm not sure. But this tree is definitely dead, I believe oak wilt but I could be wrongThat happens too!.
What I was thinking is that it looks like the upper right portion of the tree looks dead (in the photo; Post #5097), and maybe even rotten. This can break off when cutting into the trunk or driving wedges, long before the tree falls.
Philbert