The dust bowl stretched as far north as Palliser’s triangle.

I’ve dug pits near Selkirk MB, and average topsoil depth in that area is 20 cm, and the soils are regosolic (meaning it’s topsoil over top of regolith, rather than having a transitional horizon) in most farmers fields.

Go off into the bush 200 m away, and the soil there, that had the exact same pedogenic conditions has the 60 cm of Ah horizon (black topsoil), super strong structure, a fully developed B horizon (that transition horizon I mentioned earlier) and then the C (regolith).

This is all because the area lost a foot of topsoil during the 30s, and what was left was poorly managed - conventional tillage for decades - which has caused plow erosion of the B horizon and admixing of the poorer subsoil horizons into the A horizon.

This erosion of the B happens because in a conventional tillage system, you lose a few mm of soil each year off the top, yet your plow depth settings don’t change because you still need that 30 cm or whatever it is to grow your crops.