Although many of the ranges do share a common geologic history, the Pacific Coast Ranges province is not defined by geology, but rather by geography. Many of the various ranges are composed of distinct forms of rock from many different periods of geological time from the Precambrian in parts of the Little San Bernardino Mountains to 10,000-year-old rock in the Cascade Range. For one example, the Peninsular Ranges, composed of Mesozoic batholitic rock, are geologically extremely different from the San Bernardino Mountains, composed of a mix of Precambrian metamorphic rock and Cenozoic sedimentary rock. However, both are considered part of the Pacific Coast Ranges due to their proximity and similar economic and social impact on surrounding communities.