The rocks in this area comprise light-colored weak sand and mudstones overlain by darker and harder volcanic ash and lava (basalt). The red staining seen on the sandstone is a result of iron staining.
The red cliffs erode from faulting or slumping, and water seeps. After heavy rainstorms, water seeps out from between the layers and runs down the side, taking sand with it.
The cliffs are all tilted at an angle of 17 degrees, due to intense faulting in the past 10 million years as the North American and Pacific plates slide past one another. Nearby is the Garlock fault, a left-lateral strike slip fault, that is thought capable of an earthquake and has registered 35 km of offset.