IIRC, it's also a result of the pacific northwest's geology. Something about soil layering. Loam buildup over clay sub-layers. Eventually, with enough water, the upper layer just slides off - trees or no. Leastwise that's what I remember from college geology.
That is soo true. I lived close to the Oregon coast and have witnessed many trees down after a windstorm. Nothing solid to hold them in the ground.



