Geography of California

California is a U.S. state on the western coast of North America. It covers a very large area of 163,696 square miles (423,970 kilometers squared), making it one of the most geographically diverse states in the country. The state includes many different landscapes, such as the Sierra Nevada mountains, the fertile farmlands of the Central Valley, and the dry Mojave Desert in the south.

California is home to some of the most amazing trees in the world. You can find the tallest trees (coast redwood), the biggest trees (Giant Sequoia), and some of the oldest trees (bristlecone pine). The state also has both the highest point (Mount Whitney) and the lowest point (Death Valley) in the 48 contiguous states.

Generally, California is split into Northern and Southern California, though the exact boundary between the two is not always clear. Cities like San Francisco are considered Northern California, while Los Angeles is Southern California. Scientists often divide the state into eleven different areas with clear boundaries, each having its own special features.

State boundaries

The shape and edges of California were set long ago. First, Spanish explorers claimed the land as part of Alta California. In 1819, a treaty called the Adams–Onis Treaty set the northern edge at 42 degrees latitude. Later, after a war between Mexico and the United States, the Treaty of Guadalupe Hidalgo in 1848 set the southern edge about 30 miles north of where it used to be. On the east, California’s border has two straight lines: one runs north to south to the middle of Lake Tahoe, and the other angles southeast to meet the Colorado River. From there, the border follows the river to the international border near Yuma, Arizona. These borders were decided when California was preparing to become a state in 1849.

Northern California

Main article: Northern California

Northern California covers the northernmost 48 counties of the state. Major cities in this area include the San Francisco Bay Area, with cities such as San Francisco, Oakland, and San Jose, as well as the state capital, Sacramento, and its surrounding area. This region features redwood forests, the Sierra Nevada mountains—including Yosemite Valley and Lake Tahoe—Mount Shasta, and the northern part of the fertile Central Valley. The climate varies from marine and warm Mediterranean along the coast to alpine conditions in the high mountains. Besides the busy areas around the San Francisco Bay and Sacramento, Northern California has many places with fewer people. The economy here is strong in technology, clean energy, medicine, government work, and finance.

Klamath Mountains

The Klamath Mountains lie in northwest California and southwest Oregon, with the highest point being Mount Eddy in Trinity County, California. These mountains have diverse rocks and soils, leading to unique plants, including special types like Lawson's Cypress and Foxtail Pine. The weather here brings cold, snowy winters and dry, warm summers.

Cascade Range

The Cascade Range stretches from British Columbia in Canada down to Lassen Peak in California. It is part of the Pacific Ring of Fire, a area known for volcanoes. Lassen Peak, the last Cascade volcano to erupt in California, did so between 1914 and 1921. This area, close to Mount Shasta, is mostly north of the Central Valley and the Sierra Nevada mountains.

Modoc Plateau

In the northeast corner of California is the Modoc Plateau, a flat area formed from old lava flows, sitting between 4,000 and 5,000 feet above sea level. It features cinder cones, juniper flats, pine forests, and seasonal lakes. The plateau is home to animals like mule deer, elk, and pronghorn. Some parts are protected as wildlife refuges.

Basin and Range

East of the Sierra Nevada lies the Basin and Range geological province, which also extends into Nevada. This area has alternating mountains and valleys formed by the stretching of Earth's crust. Mono Lake here is North America's oldest lake. The Owens Valley is North America's deepest valley. Many dry lake beds in this area hold important salt deposits.

Coast Ranges

West of the Central Valley are the Coast Ranges, including the Diablo Range near San Francisco and the Santa Cruz Mountains south of the city. These mountains are famous for coast redwoods, the tallest trees on Earth, which grow where coastal fog reaches.

Central Valley

California's central feature is the Central Valley, a rich valley between the coastal ranges and the Sierra Nevada. The north part is the Sacramento Valley, named after its river, and the south is the San Joaquin Valley, named after its river. Both areas are watered by rivers that flow to the San Francisco Bay. Most cities here, like Stockton and Sacramento, can act as seaports because of these rivers.

Sierra Nevada

The Sierra Nevada mountain range runs north to south for 400 miles along the eastern edge of California. Mount Whitney, the highest peak in the contiguous United States, is here. The Sierra has many sunny days, warm summers, cold winters, and diverse landscapes. Famous spots include Yosemite Valley, Lake Tahoe, and huge Giant Sequoia trees. Popular trails such as the John Muir Trail and parts of the Pacific Crest Trail pass through this area, which includes Yosemite National Park, Kings Canyon National Park, and Sequoia National Park.

Southern California

Main articles: Southern California and Geography of southern California

Southern California usually means the ten southernmost counties, which are the lower one-third of the state's latitude. This area is separated from the northern part of California by mountain ranges, which have created natural barriers.

Southern California has many big cities and also large areas of open space. Over 22 million people live there, which is about 60% of California's population. Major cities include Los Angeles, Orange County, San Diego, and Riverside-San Bernardino. The area is known for its film industry, construction, entertainment, and many other jobs.

Transverse Ranges

Southern California is separated from the rest of the state by the east–west trending Transverse Ranges. These mountain ranges stretch from Point Conception to the San Jacinto Mountains in Riverside County.

The Santa Ynez Mountains are the westernmost ranges, and other ranges include the Simi Hills, Santa Monica Mountains, and San Gabriel Mountains. The highest point in these ranges is Mount San Gorgonio. It is possible to surf in the ocean and ski in the mountains on the same day in Southern California.

Mojave Desert

The Southeast of California has harsh deserts. These deserts form because mountains block moisture from the ocean, creating dry conditions. The Mojave Desert is bounded by mountain ranges and extends into Nevada. It receives very little rain each year and has high temperatures, with places like Death Valley being one of the hottest spots in the Americas.

Peninsular Ranges

The southernmost mountains of California are the Peninsular Ranges, which continue into Baja California in Mexico. These ranges include the Laguna Mountains, San Jacinto Mountains, and others. San Jacinto Peak has a cable tram that takes visitors up the mountain for hiking or skiing.

Colorado Desert

East of the peninsular ranges are the Colorado and Sonoran Deserts, which stretch into Arizona and Mexico. Some valleys here are below sea level, with Calipatria, California being the lowest community in the U.S. The Salton Sea is an inland lake formed when the Colorado River flowed into a dry area in 1905. It is California's largest lake.

Pacific Ocean

The Pacific Ocean is located to the west of California. The ocean water changes temperature from about 50 °F in the north during winter to around 70 °F in the south during summer. This smaller change in temperature happens because deep waters rise up, bringing nutrients that help many kinds of sea life grow. The waters near California are full of many types of fish, giving the sea a green color instead of the clear blue seen in some other tropical areas.

California has a very long coastline, about 840 miles, making it the third longest coastline in the United States after Alaska and Florida.

Geology

Main article: Geology of California

California has many earthquakes because of faults, especially the San Andreas Fault, along the Pacific coast. Some big earthquakes happened in 1906, 1971, 1989, and 1994. Coastal cities can also be hurt by tsunamis from undersea earthquakes. California has volcanoes too, like Lassen Peak and Mount Shasta.

Scientists study how Earth's plates move. Long ago, people thought California was an island. In the future, the sea floor might change, and California could become an island far from the mainland.

Climate

Main article: Climate of California

California has many different kinds of weather. Near the coast and in the south, it is often warm with rainy winters and dry summers. The ocean helps keep temperatures comfortable, with milder winters and cooler summers close to the water.

In winter, coastal storms can bring rain. Eastern parts of the state sometimes have thunderstorms in the summer. Because much of California is dry, wildfires can happen when it is hot and dry. Snow falls in the mountains during winter. Heavy rain or melting snow can sometimes cause flooding, and steep, unstable slopes can lead to landslides during wet weather or earthquakes.