California Geomorphic

CASCADE RANGE The Cascade Range, a chain of volcanic cones, Provinces extends through Washington and Oregon into California. KLAMATH MOUNTAINS It is dominated by Mt. The Klamath Mountains have Shasta, a glacier- rugged topography with prominent mantled volcanic cone, peaks and ridges reaching 6,000- rising 14,162 feet above 8,000 feet above sea level. In the sea level. The southern western Klamath, an irregular termination is Lassen drainage is incised into an uplifted Peak, which last erupted plateau called the Klamath pene- in the early 1900s. The plain. The uplift has left successive Cascade Range is benches with gold-bearing gravels MODOC PLATEAU transected by deep The Modoc Plateau is a on the sides of the canyons. The canyons of the Pit River. volcanic table land Klamath River follows a circuitous The river ows through (elevation 4,000- 6,000 feet course from the Cascade Range GREAT VALLEY the range between above sea level) consisting through the Klamath Mountains. The The Great Valley is an alluvial plain about 50 miles wide and these two major of a thick accumulation of province is considered to be a 400 miles long in the central part of California. Its northern volcanic cones, after lava ows and tu beds northern extension of the Sierra part is the Sacramento Valley, drained by the Sacramento winding across interior along with many small Nevada. River and its southern part is the San Joaquin Valley drained Modoc Plateau on its volcanic cones. Occasional by the San Joaquin River. The Great Valley is a trough in way to the Sacramento lakes, marshes, and which sediments have been deposited almost continuously River. sluggishly owing streams since the Jurassic (about 160 million years ago). Great oil meander across the plateau. elds have been found in southernmost San Joaquin Valley The plateau is cut by many and along anticlinal uplifts on its southwestern margin. In north-south faults. The the Sacramento Valley, the Sutter Buttes, the remnants of an province is bound inde - isolated Pliocene volcano, rise above the valley oor. nitely by the Cascade Range on the west and the Basin and Range on the east and south.

COAST RANGES The Coast Ranges are northwest-trending mountain ranges (2,000 to 4,000, occasionally 6,000 feet elevation above sea level), and valleys. The ranges and valleys trend northwest, subparallel to the San Andreas Fault. Strata dip beneath alluvium of the Great Valley. To the west is the Paci c Ocean. The coastline is uplifted, terraced and wave-cut. The Coast Ranges are composed of thick SIERRA NEVADA Mesozoic and Cenozoic The Sierra is a tilted fault block nearly 400 sedimentary strata. The miles long. Its east face is a high, rugged northern and southern multiple scarp, contrasting with the gentle ranges are separated by western slope (about 2°) that disappears a depression containing under sediments of the Great Valley. Deep the San Francisco Bay. river canyons are cut into the western slope. The northern Coast Their upper courses, especially in massive Ranges are dominated granites of the higher Sierra, are modi ed by by irregular, knobby, glacial sculpturing, forming such scenic landslide-topography of features as Yosemite Valley. The high crest the Franciscan Complex. culminates in Mt. Whitney with an elevation The eastern border is of 14,495 feet above sea level near the characterized by eastern scarp. The metamorphic bedrock strike-ridges and valleys contains goldbearing veins in the northwest in Upper Mesozoic trending Mother Lode. The northern Sierra strata. In several areas, boundary is marked where bedrock disap- Franciscan rocks are pears under the Cenozoic volcanic cover of overlain by volcanic the Cascade Range cones and ows of the Quien Sabe, Sonoma and Clear Lake volcanic BASIN and RANGE elds. The Coast Ranges The Basin and Range is the western- are subparallel to the most part of the Great Basin. The active San Andreas province is characterized by interior Fault. The San Andreas is drainage with lakes and playas, and more than 600 miles the typical horst and graben struc- long, extending from Pt. ture (subparallel, fault-bounded Arena to the Gulf of ranges separated by downdropped California. West of the basins). Death Valley, the lowest area San Andreas is the in the United States (280 feet below Salinian Block, a granitic sea level at Badwater), is one of these core extending from the grabens. Another graben, Owens southern extremity of Valley, lies between the bold eastern the Coast Ranges to the fault scarp of the Sierra Nevada and north of the Farallon Inyo Mountains. The northern Basin Islands. and Range Province includes the Honey Lake Basin.

TRANSVERSE RANGES The Transverse Ranges are an east-west trending series of steep mountain ranges and valleys. The east-west structure of the Transverse Ranges is oblique to the normal northwest trend of coastal California, hence the name "Transverse." The province extends oshore to include San Miguel, Santa Rosa, and Santa Cruz islands. Its eastern extension, the San Bernardino Moun- tains, has been displaced to the south along the San Andreas Fault. Intense north-south compression is squeezing the Transverse Ranges. As a result, this is one of the most rapidly rising regions on earth. Great thicknesses of Cenozoic petroleum-rich sedimentary rocks have been folded and faulted, making this one of the important oilproducing areas in the United States.

PENINSULAR RANGES A series of ranges is separated by northwest trending valleys, subparallel to faults branching from the San Andreas Fault. The trend of topogra- MOJAVE DESERT phy is similar to the Coast Ranges, but The Mojave is a broad interior region the geology is more like the Sierra of isolated mountain ranges Nevada, with granitic rock intruding separated by expanses of desert the older metamorphic rocks. The plains. It has an interior enclosed Peninsular Ranges extend into lower drainage and many playas. There are California and are bound on the east COLORADO DESERT two important fault trends that by the Colorado Desert. The Los A low-lying barren desert basin, control topography a prominent Angeles Basin and the island group about 245 feet below sea level in NW-SE trend and a secondary (Santa Catalina, Santa Barbara, and the part, is dominated by the Salton east-west trend (apparent alignment distinctly terraced San Clemente and Sea. The province is a depressed with Transverse Ranges is signi cant). San Nicolas islands), together with the block between active branches of The Mojave province is wedged in a surrounding continental shelf (cut by alluvium-covered San Andreas sharp angle between the Garlock deep submarine fault troughs), are Fault with the southern extension Fault (southern boundary Sierra included in this province. of the Mojave Desert on the east. Nevada) and the San Andreas Fault, It is characterized by the ancient where it bends east from its north- beach lines and silt deposits of west trend. The northern boundary of extinct Lake Cahuilla. the Mojave is separated from the prominent Basin and Range by the eastern extension of the Garlock Fault.

Descriptions and Boundaries courtesy of California Geological Survey