An interesting crack in a poplar

A few months ago, I came across this sight whilst looking at a few larger poplars nearby. Evidently some form of shear crack, I would suspect (consulting Mattheck’s work), though as the crack is on the tension side of the lean, and the tree is leaning with the prevailing wind, I’m trying to wrap my head around exactly how such a crack manifested. Wonder aside, this is a good example of a crack in a tree, and therefore I thought I’d share it with you all! If anyone has any more concrete ideas than me, please share them below in the comment section.

Here we can see the tree as a whole, with its very significant lean.

A closer look allows us to really begin to observe the crack that has manifested.

Not a fresh crack, I would say. Here, we can see how it terminates down in a tension root.