The hills in back of Cal Poly have a serpertinite rock outcrop on the ridge tops. Two soils form here among the rocks, Cuesta and Henneke. The area supports many endemic plant species such as the bunch grasses and yucca plants seen here. The difference between the two soils is in their depth. The Cuesta soil is over 19 inches in depth. The soil is poorly suited for farming or grazing. It is typical of Land Capability class VII.