In USDA soil taxonomy, Orthents are defined as Entisols that lack horizon development due to either steep slopes or parent materials that contain no permanent weatherable minerals (such as ironstone). Typically, Orthents are exceedingly shallow soils. They're often referred to as "skeletal soils" or, in the FAO soil classification, as Lithosols. The basic requirement for recognition of an orthent's that any former soil has been either completely removed or so truncated that the diagnostic horizo… (More on Orthent)