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thumb|upright=1.5|Map of California topography and geomorphic provinces
thumb|upright=1.5|California's major mountain ranges
California is a U.S. state on the western coast of North America. Covering an area of , California is among the most geographically diverse states. The Sierra Nevada, the fertile farmlands of the Central Valley, and the arid Mojave Desert of the south are some of the geographic features of this U.S. state. It is home to some of the world's most exceptional trees: the tallest (coast redwood), most massive (Giant Sequoia), and oldest (bristlecone pine). It is also home to both the highest (Mount Whitney) and lowest (Death Valley) points in the 48 contiguous states.
The state is generally divided into Northern and Southern California, although the boundary between the two is not well defined. San Francisco is decidedly a Northern California city and Los Angeles is a Southern California one but areas in between do not often share their confidence in geographic identity. The US Geological Survey defines the geographic center of California about 7.1 miles (11.4 km) driving distance from the United States Forest Service office in the community of North Fork. Earth scientists typically divide the state into eleven geomorphic provinces with clearly defined boundaries. They are, from north to south, the Klamath Mountains, the Cascade Range, the Modoc Plateau, the Basin and Range, the Coast Ranges, the Central Valley, the Sierra Nevada, the Transverse Ranges, the Mojave Desert, the Peninsular Ranges, and the Colorado Desert.
State boundaries
The boundaries of California were defined by Spanish claims of Mexico, as part of the province of Alta California. The northern boundary of Spanish claims was set at 42 degrees latitude by the Adams–Onis Treaty of 1819. The states of Nevada and Utah, also originally part of Alta California, also use that line for their northern boundaries. The southern boundary, between California and Mexico, was established by the Treaty of Guadalupe Hidalgo that ended the Mexican–American War in 1848. The line is about north of the former Alta California southern boundary. The eastern boundary consists of two straight lines: a north–south line from the northern border to the middle of Lake Tahoe, and a second line angling southeast to the Colorado River. From that point, south-southwest of Davis Dam on Lake Mohave, the southeast boundary follows the Colorado River to the international border west of Yuma, Arizona. The eastern and south-eastern boundaries were decided upon during the debates of the California Constitutional Convention in 1849.
Northern California
thumb|upright=1.6|Mount Shasta from [[Interstate 5]]
Northern California usually refers to the state's northernmost 48 counties.
The main population centers of Northern California include San Francisco Bay Area (which includes the cities of San Francisco, Oakland, and the largest city of the region, San Jose), and Sacramento (the state capital) as well as its metropolitan area. It also contains redwood forests, along with the Sierra Nevada including Yosemite Valley and Lake Tahoe, Mount Shasta (the second-highest peak in the Cascade Range after Mount Rainier in Washington), and the northern half of the Central Valley, one of the world's most productive agricultural regions. The climate can be generally characterized by its marine to warm Mediterranean climates along the coast, to a somewhat continental Mediterranean climate in the valley to alpine climate zones in the high mountains. Apart from the San Francisco Bay Area and Sacramento metropolitan areas (and some other cities in the Central Valley), it is a region of relatively low population density. Northern California's economy is noted for being the de facto world leader in industries such as high technology (both software and semiconductor), as well as being known for clean power, biomedical, government, and finance.
Klamath Mountains
thumb|upright|Alpine tarn in the [[Trinity Alps]]
The Klamath Mountains are a range in northwest California and southwest Oregon, the highest peak being Mount Eddy in Trinity County, California, at . The range has a varied geology, with substantial areas of serpentine and marble. The climate is characterized by moderately cold winters with heavy snowfall and warm, very dry summers with limited rainfall. As a consequence of the geology, the mountains have a unique flora, including several endemic or near-endemic species, such as Lawson's Cypress (Chamaecyparis lawsoniana) and Foxtail Pine (Pinus balfouriana). Brewer's Spruce (Picea breweriana) and Kalmiopsis (Kalmiopsis leachiana) are relict species, remaining since the last ice age.
Cascade Range
The Cascade Range is a mountainous region stretching from the Fraser River in British Columbia, Canada down to south of Lassen Peak, California. The Cascades (as they are called for short) are part of the Pacific Ring of Fire, the ring of volcanoes around the Pacific Ocean. All of the known historic eruptions in the contiguous United States have been from either Cascade volcanoes or near Mono Lake. Lassen Peak was the last Cascade volcano to erupt in California, from 1914 to 1921. Lassen is the most southerly active volcano of the Cascade chain.
This region is located in the northeastern section of the state bordering Oregon and Nevada, mostly north of the Central Valley and the Sierra Nevada mountain range. The area is centered on Mount Shasta, near the Trinity Alps. Mount Shasta is a dormant volcano, but there is some evidence that it erupted in the 18th century. The plateau lies between the Cascade Range to the west and the Warner Mountains to the east. The Lost River watershed drains the north part of the plateau, while southern watersheds either collect in basin reservoirs or flow into Big Sage Reservoir and thence to the Pit River.
Nine percent of the plateau is protected as reserves or wilderness areas, The plateau supports large herds of mule deer (Odocoileus hemionus), Rocky Mountain Elk (Cervus canadensis), and pronghorn (Antilocapra americana). One notable feature of the Basin and Range is Mono Lake, which is the oldest lake in North America. The Basin and Range also contains the Owens Valley, the deepest valley in North America (more than 10,000 feet (3 km) deep, as measured from the top of Mount Whitney).
In the eastern part of the state, below the Sierra Nevada, there is a series of dry lake beds that were filled with water during the last ice age (fed by ice melt from alpine glaciers but never directly affected by glaciation; see pluvial). Many of these lakes have extensive evaporite deposits that contain a variety of different salts. In fact, the salt sediments of many of these lake beds have been mined for many years for various salts, most notably borax (this is most famously true for Owens Lake and Death Valley).
In this province reside the White Mountains, which are home to the oldest living organism in the world, the bristlecone pine
Coast Ranges
thumb|upright=1.6|Skyline Boulevard, along the crest of the Santa Cruz Mountains
To the west of the Central Valley lies the Coast Ranges, including the Diablo Range, just east of San Francisco, and the Santa Cruz Mountains, to the south of San Francisco. The Coast Ranges north of San Francisco become increasingly foggy and rainy. These mountains are noted for their coast redwoods, the tallest trees on earth, which live within the range of the coastal fog.
Central Valley
California's geography is largely defined by its central feature—the Central Valley, a huge, fertile valley between the coastal mountain ranges and the Sierra Nevada. The northern part of the Central Valley is called the Sacramento Valley, after its main river, and the southern part is called the San Joaquin Valley , after its main river. The whole Central Valley is watered by mountain-fed rivers (notably the San Joaquin, Kings, and Sacramento) that drain to the San Francisco Bay system. The rivers are sufficiently large and deep that several inland cities, notably Stockton, and Sacramento are seaports.
The southern tip of the valley has interior drainage and thus is not technically part of the valley at all. Tulare Lake, with an area of , once filled much of the area. In modern times, it is usually a dry lake and partially covered with agricultural fields. The lake reappears during unusually high levels of rainfall or snow melt such as the winter of 2022 and early spring of 2023.
Sierra Nevada
thumb|[[Rock Creek (Owens River)|Little Lakes Valley in the eastern Sierra Nevada]]
In the east of the state lies the Sierra Nevada, which runs north–south for . The highest peak in the contiguous United States, Mount Whitney at 14,505 feet (4.42 km), lies within the Sierra Nevada. The topography of the Sierra is shaped by uplift and glacial action.
The Sierra has 200–250 sunny days each year, warm summers, fierce winters, and varied terrain, a rare combination of rugged variety and pleasant weather. The famous Yosemite Valley lies in the Central Sierra. The large, deep freshwater Lake Tahoe lies to the North of Yosemite. The Sierra is also home to the Giant Sequoia, the most massive trees on Earth.
The most famous hiking and horse-packing trail in the Sierra is the John Muir Trail, which goes from the top of Mount Whitney to Yosemite valley. This is part of the Pacific Crest Trail that goes from Mexico to Canada. The three major national parks in this province are Yosemite National Park, Kings Canyon National Park, and Sequoia National Park.