Cima Dome and Volcanic Field

Cima Dome and Volcanic Field
Name	Cima Dome and Volcanic Field
Photo caption	Cima Dome region, Mojave Desert
Elevation	~1,800–1,900 m
Location	San Bernardino County, California, Mojave Desert, United States
Type	Volcanic field, shield-like dome, cinder cones, lava flows
Age	Pleistocene–Holocene
Last eruption	Late Pleistocene to Holocene (youngest vents)

Cima Dome and Volcanic Field

Cima Dome and Volcanic Field is a distinctive volcanic landscape in the eastern Mojave Desert of San Bernardino County, California, near the Kelso Dunes and Mojave National Preserve. The area comprises a broad, dome-shaped swath of closely clustered volcanic vents, shield-like profiles, and extensive basalt and andesite lava flows that record mid- to late-Quaternary magmatism. Its geomorphology, petrology, and human associations link regional tectonics, paleoenvironmental change, and historic use by Indigenous peoples and federal agencies.

Geography and Setting

The dome sits within the Mojave National Preserve adjacent to the Cima Road corridor and is bounded by the Ivanpah Valley to the southeast and the Sierra Nevada–Mojave Desert transition to the west. Nearby landmarks include the Cima Volcanic Field's cluster of cinder cones, the Cima Dome Road access, and the railroad at Cima (a former whistle stop). Elevations on the dome reach approximately the height of Kelso Mountain and are intercalated with bajadas draining toward the Hector Road corridor and Soda Lake (Mojave). Regional infrastructure such as Interstate 15, historic Route 66, and the Union Pacific Railroad provide reference points for access and research logistics.

Geology and Volcanic History

The volcanic architecture records extensional tectonics associated with the broader Basin and Range Province and the eastern Transverse Ranges margin. Volcanism produced a pile of overlapping shield edifices, spatter and scoria cones, and ʻaʻā and pahoehoe lava flows under conditions influenced by lithospheric thinning linked to the San Andreas Fault system and the Garlock Fault system. The field overlies metamorphic and granitic basement rocks related to the Mesozoic magmatic arc and is crosscut by faults mapped by the United States Geological Survey. Volcanic deposits interfinger with alluvial fan sediments correlated with Pleistocene climatic cycles and playa deposits of the Mojave River system.

Petrology and Geochemistry

Magmatic products range from olivine-phyric basalts to more evolved basaltic andesites, with phenocryst assemblages dominated by olivine, pyroxene, and lesser plagioclase. Whole-rock geochemistry shows typical alkaline to transitional signatures and trace-element patterns consistent with small-degree partial melting of a mantle source modified by lithospheric mantle metasomatism. Isotopic ratios in published studies compare with other Basin and Range and Colorado River province lavas, reflecting mantle heterogeneity similar to fields studied near Cima Volcanic Field, Amboy Crater, and Lava Beds National Monument. Geochemical trends indicate open-system processes including fractional crystallization and limited crustal assimilation.

Chronology and Eruption History

Radiometric ages from potassium-argon and argon-argon dating place the bulk of eruptions in the middle to late Pleistocene, with some vents yielding ages that span from ~1.5 million years to younger Late Pleistocene eruptions. The youngest eruptive centers have surface features and thermoluminescence signatures implying eruptive activity persisted into the late Pleistocene and possibly the earliest Holocene, contemporaneous with climatic shifts recorded in nearby Lake Manix and Owens Lake basin sediments. Stratigraphic relationships with Alluvium and tephra layers allow correlation with regional volcanic episodes such as those preserved at Cinder Cone (Lassen), and aid reconstruction of eruptive volumes and dispersal.

Ecology and Climate

Cima Dome lies within the high-elevation ecological gradients of the Mojave Desert, where vegetation communities include Joshua Tree National Park-type Yucca brevifolia stands at lower slopes transitioning to blackbrush and shrub steppe assemblages on basaltic substrates. Soils developed on volcanic deposits support cryptobiotic crusts and endemic invertebrate assemblages similar to those documented in the Desert Tortoise National Recovery Plan literature and faunal lists for the Mojave National Preserve. The climate is arid continental with pronounced diurnal ranges; paleoclimatic reconstructions from pollen and lacustrine deposits indicate cooler wetter intervals during glacial maxima that influenced eruption preservation and biotic colonization.

Human History and Cultural Significance

The volcanic landscapes were traversed and used by Indigenous groups including Chemehuevi, Serrano, and Mojave peoples, who left lithic scatters and trade-route evidence linking to the Colorado River corridor. Euroamerican exploration, mining prospecting, and railroad construction in the 19th and 20th centuries altered access patterns; historical place names and railroad depots such as Cima, California reflect this era. The region figures in federal conservation planning associated with the establishment of the Mojave National Preserve and has been the subject of archaeological survey under mandates of the National Historic Preservation Act and management practices by the National Park Service.

Conservation and Land Management

Management falls primarily under the National Park Service within the Mojave National Preserve, with additional oversight by the Bureau of Land Management for adjacent lands and the California Department of Fish and Wildlife for species protections. Conservation strategies emphasize protection of volcanic landforms, archaeological sites, and desert tortoise habitat pursuant to consultations under the Endangered Species Act and interagency plans with Federal Highway Administration and Union Pacific Railroad stakeholders. Ongoing research partnerships with universities and the United States Geological Survey aim to refine eruption chronologies, geochemical datasets, and climate-vegetation interactions to inform adaptive management.

Category:Volcanic fields of California Category:Landforms of San Bernardino County, California