Last tree I fell last week end was a fire killed bucksking willow. 24" DBH and about 55' tall. Brushed out the top and cut up down just past the first (from the butt) crotch. That left about 25' of clear log. While I was splitting and loading the top, I could heard popping and saw a horizontal crack propagating down the log. Had my back turned when there was a BANG. Turned to look and the crack had split open for at least 15 ft and was gaping about 6". Loaded a few more and another loud pop, looked. The log had this time split vertically neatly quartering itself. Proceeded to block about 8' at a time and load, each time the two splits would progress further down. That continued until all that I had to split were the last 4 rounds at the butt. 3/4 cord on the truck in 3 hours.
30 years at this and that's the first time I ever saw that happen. Can't feature what caused the stress, log only had a slight curve to it and was near vertical as grown. Not only did I have an easy few hours, I also got to make the 041 work hard.