Desert Soils

I am not sure you can classify the desert soils as dirt. The absence of water results in little or no chemical weathering of the soil. As you can see from this cross-section the topmost layer is hard and cemented with caliche (salt). The white band at the top of the soil layers is the cemented portion of the soil. Normally, geologists would define soil as the loose uppermost part of the bedrock, but in the desert the soil can be as hard as the subsurface rock. This particular picture demonstrates the mountain and basin desert of southern Arizona. The rocks and clay are typical of the intermontane basins.