Los Alamos soils are underlain at depths of 20 to 40 inches by pumice deposits. Maysdorf soils have hue of 2.5Y or 10YR in the lower part of the Bt horizon. Millett soils have gravelly and very gravelly C horizons. Penistaja soils have more than 35 percent fine or coarser sand in the B2t horizon. Bk horizons above 40 inches.
Potts soils are on alluvial fans, benches, cuestas, and valley-filling sideslopes.
Slopes range from 0 to 20 percent. Elevation is 5,000 to 7,500 feet. The soils formed in calcareous reddish brown sediments of low aggregate stability derived principally from redbed shale and sandstone. At the type location average annual precipitation is 12 to 16 inches with peak periods of precipitation occurring during the spring and summer. The frost-free season is 95 to 125 days.