These areas tend to have gentle to steep slopes with an old rock base, mostly from the Mesozoic epoch. They are built upon both felsic and mafic rock formations.

The southern and Central Sierra Oak woodlands have a granite-based soil, the Northern Sierras have volcanic soil, and the Coastal Ranges have sedimentary soil.

Water runoff from the tops of mountains comes through these ecosystems, so they act as a natural water purifier. Their watersheds drain into different streams and can even create new streams if there are large amounts of rainfall.

Fire is a natural part of oak-woodland ecosystems and influences community structure, nutrient cycling, habitat, and available food. The extent of the impact that a fire can have is determined by the frequency, timing, intensity, and landscape complexity. Fire is also important because it reduces ladder fuels and it kills diseases and pests that have the potential to infest oaks.

Earthquakes are a common occurrence in California, with the largest fault in Southern California being the San Andrea's Fault. Usually, earthquakes do not impact oak trees since the trees move with the ground. Although stronger earthquakes may cause the breaking of branches and tree crowns, loosening of root systems in the soil, and in the worst-case tree falling.