Its called Loess. It has surprising strength, undisturbed. Once disturbed from its original formation though, not so much. That explains the fragility you mention. Bet it heals quickly though.The soil here is pretty soft. It doesn't take long to dig a 16" post hole down about three feet. If you find a rock in the soil it was put there by someone. Like an old building foundation. In one area of my property you find yellow sand about 6'-8' down. Makes me think that the valley near by was a lake several million years ago. I was told that the deep top soil in this area was blown in by a wind storm millions of years ago. That must have been a pretty intense storm to blow that much dirt.