The Lava Mountains are a mountain range located along the northern edge of the

Mojave Desert The Mojave Desert (; ; ) is a desert in the rain shadow of the southern Sierra Nevada mountains and Transverse Ranges in the Southwestern United States. Named for the Indigenous peoples of the Americas, indigenous Mohave people, it is located pr ...

, in

San Bernardino County San Bernardino County ( ), officially the County of San Bernardino and sometimes abbreviated as S.B. County, is a county located in the southern portion of the U.S. state of California, and is located within the Inland Empire area. As of th ...

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 ...

. They are one of the eastern limits of the

Fremont Valley The Fremont Valley is a valley located in the western Mojave Desert of California. It stretches from the town of Mojave approximately 70 km northeast to the foothills of the Lava Mountains and Summit Range. The valley is home to Koehn Dr ...

. They span the northwestern portion of the Golden Valley Wilderness, which sits between it and the Almond Mountains on the southeastern side. The mountain range is cut by several deep-walled canyons with distinctive layers of multicolored sedimentary rocks. The peak of the mountain range is at around 5,000 feet on Dome Mountain.

Geology

The mountains are located along the

Garlock Fault The Garlock Fault is a left-lateral strike-slip fault running northeast–southwest along the north margins of the Mojave Desert of Southern California, for much of its length along the southern base of the Tehachapi Mountains. Geography Stret ...

. The Blackwater fault passes through the southwestern part of the area, and the Brown's Ranch fault zone and its associated faults pass through the western part. The pre-

Tertiary Tertiary (from Latin, meaning 'third' or 'of the third degree/order..') may refer to: * Tertiary period, an obsolete geologic period spanning from 66 to 2.6 million years ago * Tertiary (chemistry), a term describing bonding patterns in organic ch ...

rocks in the area mainly consist of

quartz monzonite Quartz monzonite is an intrusive, felsic, igneous rock that has an approximately equal proportion of orthoclase and plagioclase feldspars. It is typically a light colored phaneritic (coarse-grained) to porphyritic granitic rock. The plagioclase ...

. The major sedimentary unit is the Bedrock Spring Formation, which is chiefly composed of arkosic sandstone and conglomerate, as well as some silstone and

brecciated Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a varie ...

volcanic rocks. That formation is overlain by the Almond Mountain volcanics and the Klinker Mountain volcanics in the eastern and western parts of the region, respectively. Overlying these are flows of Lava Mountains

andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...

dating to the late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

gravels Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentary and erosive geological processes; it is also produced in large quantities commercially as crushed stone. Gravel is classified by p ...

alluvium Alluvium (, ) is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is ...

, and

travertine Travertine ( ) is a form of terrestrial limestone deposited around mineral springs, especially hot springs. It often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and rusty varieties. It is formed by a process ...

. All of the volcanic rocks in the area are

plagioclase Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continu ...

porphyries.

References

Mountain ranges of the Mojave Desert Mountain ranges of Southern California Mountain ranges of San Bernardino County, California {{SanBernardinoCountyCA-geo-stub