The entirety of Annadel was below the ocean floor as recently as twelve million years ago, around which time massive uplift and volcanic action formed the massif which comprises the park of today. Elevations in Annadel range from about above sea level. Slopes within Annadel commonly range from 15 to 30 percent, but it is not uncommon to encounter slopes up to 70 percent on steep slopes above drainages which are covered in douglas fir forest. One of the major soil associations within the park is Goulding cobbly clay loam, which contains roughly 25 percent cobblestones with some basaltic exposures, evidence of the volcanic origins of the Sonoma Mountains. Typical soil depths are . Much of the soil type in the Yulupa Creek riparian zone consists of Laniger loam, with rhyolite outcrops, another relic of the igneous history.