I found Susan's website awhile ago after reading her column in the Spokane paper.
If I understand right, she has no rocks in her soil. That means, she is in the Palouse Hills or Peone Prairie or somewhere with windblown, loess soil. Honestly, I think that is half of my soil. The other half is, of course, the gravel.
@Glenpicardmom said rocks and sand, I believe. Along what must have been the shoreline or where the water slowed during the glacial flooding, lots of sand was deposited.
The floods moved boulders but it didn't result in terrible soil everywhere. Pulverized basalt isn't a terrible thing. Where the wind could lift it, the result was "scabland." Where the dust was deposited, are dryland grain farms, even some fruit orchards, where water can get to it.
I was down in Oregon's Multnomah Valley for Christmas. The soil of that very fertile farmland is there partly because of those prehistoric floods carrying soil up that valley as the water slowed, stymied by the Coastal Mountains and escape to the Pacific.
Steve