What makes a tree 'decide' to split when it does? The crack was
   like a sonic boom, and we didn't know if the roof was collapsing
   or a tree breaking for a split second, but jumping 2 feet out of
   the way, along with some folks behind us, we had good luck on
   our side. Why then? A weakened tree just sits, looking, well,
   sturdy as a tree and suddenly, a gust of wind, a butterfly
   farts, a squirrel drops his nuts - all I know is this: whatever
   we were thinking about before that moment, for several people
   this day, was completely gone. Interesting bit of randomness for
   today. Thank you for not hurting us, tree. I guess you'd been
   hanging on long enough and it was time for you to "split"