Living in western Washington, we do have a diverse soil system.
I work all over as an operating engineer, and the soils run from pure blue clay to solid rock. I was cutting a road in between renton and issaquah and ran into what looked like burnt wood in the rock I was loading. Low and behold a block of wood rolled out of the cut. It is about 2 1/2 ft through and 3ft tall. I was so surprised to find petrified wood on the west side of the cascades. I know there is a lot on the east side and is colorful, but the west side is just kind of a dark color. There is some small beads in it that look like bug eggs. White and in a cluster. I did some investigation about it and found that to get petrified wood it has to be covered with ash. So I expect that Mt. Rainier had dumped several ft as I was down about 10 when I found it.