California

California's Physical Environment

California is perhaps unmatched anywhere in the world in geologic diversity and access to good exposures. Located at the base of the Santa Monica Mountains, five miles from the Pacific Ocean, UCLA is within commuting distance of the sea, desert, and large (and growing) mountain ranges. Local geoscientists can step across the San Andreas fault from one crustal plate to another. UCLA offers incomparable opportunities to study earth and space sciences in a Mediterranean climate, cooled by ocean breezes. The surrounding communities of Beverly Hills, Bel Air, Brentwood, and Santa Monica attest to the pleasantness of the environs.

Precambrian and Paleozoic sedimentary rocks occur in eastern California. In the north of the State lie the impressive cones of Mt. Shasta and Lassen Peak, and some of the world's largest exposures of upper-mantle ultramafic bodies. To the south of UCLA is the largely unstudied Baja Peninsula and the actively rifting Gulf of California. Precambrian basement rocks, including anorthosites, crop out nearby in the San Gabriel and San Bernardino Mountains. Eastward in the Mojave Desert, delineated by the active San Andreas and Garlock faults, are Precambrian granitic rocks, Mesozoic granitic plutons, and cones and flows of basanite and alkali basalt. These latter contain mantle and crustal xenoliths and include some of the youngest basaltic volcanoes in the continental United States.

The thickest section of marine diatomites in the world occurs in the coastal region. The Great Valley forearc basin is the most thoroughly studied and best understood ancient basin of its type in the world. The Franciscan complex of the Coastal Ranges is a low-temperature, high-pressure, metamorphosed accretionary prism formed during Mesozoic and early Cenozoic plate convergence. Paralleling this range to the east are the high-temperature, low-pressure metavolcanic rocks of the Sierra Nevadabatholith. These two areas present the classic paired metamorphic belts so characteristic of the circum-Pacific region, nowhere else as well exposed or as well preserved.

Quaternary sedimentary deposits and volcanic rocks are widespread throughout southern California, and are commonly folded and faulted. Owing to the rapid rates of uplift and the great diversity of climate, geomorphic processes are unusually active and varied.