The Santa Lucia Preserve ranges in elevation from a low of 30 feet to nearly 3,000 feet at the summit of Halls Ridge. The bedrock of the Preserve is granitic and is a portion of the Pacific (crustal) Plate known as the Salinian Block, which is separated from the North American Plate by the nearby San Andreas fault, and is actively moving northwest along this faultline. This movement has caused considerable pressure, folding, faulting, and uplift over the last 5 million years and created the abrupt and rugged terrain of the Santa Lucia Mountains. Surface rocks on the Preserve include granitic, sedimentary, and volcanic rocks. The valleys and creek floodplains contain sandy and loamy alluvial deposits.