Native American culture in many parts of California is preserved in fragmentary oral and conventional written histories, but also in sometimes dramatic petroglyphs and pictographs throughout the state. The symbolism of these images has been interpreted to reflect the natural environment, in particular issues related to rain. Although there is little doubt that rain was of paramount concern to native tribes, I suggest that geological context also played an important role in shaping early spiritual beliefs in general, and petroglyph sites in particular. From the standpoint of Native American philosophies and spiritual beliefs, geological unrest is not merely a reflection but in some cases an actual embodiment of the spiritual world. To understand the significance of petroglyph sites, they must be considered in the context of overall Native American beliefs. In this context, sites of repeated geological unrest would invariably have evolved great spiritual significance. Petroglyph locations and ages may thus provide independent age controls on 'prehistoric' earthquakes in California. ?? The Geological Society of London 2007.