The Chocolate Mountains of

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

are located in Imperial and Riverside counties in the

Colorado Desert The Colorado Desert is a part of the larger Sonoran Desert located in California, United States, and Baja California, Mexico. It encompasses approximately , including the heavily irrigated Coachella, Imperial and Mexicali valleys. It is home to ...

Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural List of regions of California, region that generally comprises the southern portion of the U.S. state of California. Its densely populated coastal reg ...

. The mountains stretch more than 60 miles (100 km) in a northwest to southeast direction, and are located east of the

Salton Sea The Salton Sea is a shallow, landlocked, highly salinity, saline endorheic lake in Riverside County, California, Riverside and Imperial County, California, Imperial counties in Southern California. It lies on the San Andreas Fault within the S ...

and south and west of the Chuckwalla Mountains and the

Colorado River The Colorado River () is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and in northern Mexico. The river, the List of longest rivers of the United States (by main stem), 5th longest in the United St ...

. To the northwest lie the Orocopia Mountains.

Geography

The Chocolate Mountains form the northeast boundary of the

Salton Trough The Salton Trough is an active tectonic pull-apart basin, or graben. It lies within the Imperial, Riverside, and San Diego counties of southeastern California and extends south of the Mexico–United States border into the state of Baja Califo ...

extending as a narrow range some southeast from the Orocopia Mountains to the

valley.Singer, Eugene, ''Geology of the Imperial Valley''
/ref> The mountains are located about west of the Chocolate Mountains of

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

, but the two ranges are not connected. The range reaches an elevation of 2,475 feet (754 m) at Mount Barrow, and serves as a

drainage divide A drainage divide, water divide, ridgeline, watershed, water parting or height of land is elevated terrain that separates neighboring drainage basins. On rugged land, the divide lies along topographical ridges, and may be in the form of a single ...

for the Salton Watershed to the west. The mountains receive very little rainfall in a normal year, typically 4-6 inches (100 to 150 mm). The predominant natural plants are of the creosote bush–white bursage community, and the mean annual temperature is about to .

Geology

The range is composed of Precambrian basement rocks and Orocopia Schist with

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

granite intrusions. The range may have been formed by the collision of a microcontinental fragment with mainland Southern California during the Late Cretaceous. The collision is indicated by a

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. I ...

which emplaced

Proterozoic The Proterozoic ( ) is the third of the four geologic eons of Earth's history, spanning the time interval from 2500 to 538.8 Mya, and is the longest eon of Earth's geologic time scale. It is preceded by the Archean and followed by the Phanerozo ...

and

rocks of

continental crust Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as '' continental shelves''. This layer is sometimes called '' si ...

on top of the late Mesozoic Orocopia Schist which in turn was composed of oceanic sedimentary and volcanic rocks. The range was host to numerous small

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

workings in the 19th century with one, the Mesquite Mine to the east, continuing to be active into the 20th century.

History

The Bradshaw Trail passed by the side of the mountains, the first "euroamerican" route to the

from

Riverside, California Riverside is a city in and the county seat of Riverside County, California, United States. It is named for its location beside the Santa Ana River. As of the 2020 census, the city has a population of 314,998. It is the most populous city in th ...

Military closures

The mountain range is occupied by the Chocolate Mountain Aerial Gunnery Range, an aerial and gunnery practice area used by the

United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

and

Marines Marines (or naval infantry) are military personnel generally trained to operate on both land and sea, with a particular focus on amphibious warfare. Historically, the main tasks undertaken by marines have included Raid (military), raiding ashor ...

. A large part of the Chocolate Mountains lies within the gunnery range, and is closed to the public.

Wilderness areas

Little Picacho Wilderness

At the southeastern end of the Chocolate Mountains range are two important wilderness areas. The first is the Little Picacho Wilderness, a 38,170 acre (154.5 km²) region of geological features and habitat protection under the direction of the

Bureau of Land Management The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands, U.S. federal lands. Headquartered in Washington, D.C., the BLM oversees more than of land, or one ...

. The preserve has within its boundaries the southern portion of the Chocolate Mountains. Elevations within this area range from 200 to . The topography, characterized by jutting spires and steep ridges, is quite dramatic. Ravines laced within the range gradually broaden into sandy, tree-lined washes. Slopes and plains are devoid of vegetation, instead covered with a desert pavement of angular cobbles. These rusty dark orange and brown colored cobbles stand out against the nearly white bottoms of the washes. It is also called the Little Picacho Peak Wilderness.

Indian Pass Wilderness

The Indian Pass Wilderness Area is to the north with of open space. The Indian Pass Wilderness is a distinctive part of the Chocolate Mountains, a range which extends from south central Riverside County to the

near Yuma, Arizona. Quartz Peak is the highest point in the wilderness capped at . Jagged peaks and spires are sliced by mazes of twisting canyons which carry water from occasional desert cloudbursts into several tree-lined washes. One of these washes passes through the heart of the wilderness area, giving rise to the region's local name, "Julian Wash country." The area's proximity to the Colorado River and the Arizona Desert contribute to the presence of wildlife species not commonly found in the California Desert.Indian Pass
Retrieved June 22, 2010. At the southern end of the Chocolate Mountains at elevations from 200 to , the Indian Pass Wilderness preserve is located east of Brawley, California, and is also managed by the Bureau of Land Management. A herd of 25 desert bighorn sheep reside in the wilderness area, along with "the Picacho

feral horse A feral horse is a free-roaming horse of domesticated stock. As such, a feral horse is not a wild animal in the sense of an animal without domesticated ancestors. However, some populations of feral horses are managed as wildlife, and thes ...

s," wild burros, and the native and endangered

desert tortoise The desert tortoise (''Gopherus agassizii'') is a species of tortoise in the Family (biology), family Testudinidae. The species is native to the Mojave Desert, Mojave and Sonoran Deserts of the southwestern United States and northwestern Mexico ...

and spotted bat.