Soils and geology are closely linked. The soils found on Poly Land have developed from four parent materials. Along Brizzolari and Stenner Creeks is and area of nearly level soils developed from alluvium (water deposited parent materials). The soils found on the alluvium include Mocho, Cropley and Salinas. Most of the area is mapped as Salinas.

On the uplands are soils that have formed on sandatone and shale. The Los Osos soil has developed on the sandstone while the Diablo has formed on exposures of shale. Both the Diablo and Los Osos soils have high shrink swell potentials that limit their use for development. The Lodo soil has developed on the meta-volcanic rocks lying next to the serpentinite formation capping the ridgetops. Associated with the Lodo are areas of much more shallow but related soils identified as Lompico and McMullin. The areas on the hills in back of campus having these soils are commonly vegetated by black sage.

Two soils are commonly associated with the Serpentinite intrusive rock parent materials. They are Cuesta and Henneke. The Cuesta series is deeper than the shallow Henneke series. Depths of the two range from over 19 inches for the Cuesta and less for the Henneke. Both soils support a unique suite of endemic plants.