Tectonically, Owens Valley is a graben formed by the movement of the Sierra Nevada-Great Valley block with respect to the rest of North America. Farther south lies the Coso volcanic field, which is also geothermally active unlike Big Pine volcanic field. Various processes have been proposed to explain the volcanism in the Basin and Range province. These include tectonic spreading which triggered the upwelling of mantle material, convection within the mantle owing to temperature and viscosity differences, the aftereffects of Proterozoic crustal boundaries, mantle currents and release of water by the slab of the Farallon Plate and the delamination of crustal material. There are a number of volcanic fields in Eastern California and Big Pine is one of these. Volcanic activity at Big Pine and Coso volcanic fields is linked to the tectonic spreading of the Basin and Range province, and vents at Big Pine are associated with faults such as the Owens Valley fault, the Sierra Nevada fault and the White Mountains fault; faults have offset lava flows of the field. Seismic imaging of the crust beneath the Big Pine volcanic field indicates that the lithosphere is thinner there than elsewhere. The Big Pine volcanic field has erupted basaltic rocks spanning a range of composition from alkali basalt to basanite, as well as one unit of silicic rocks. Phenocrysts include olivine, plagioclase and clinopyroxene. The erupted rocks also contain xenoliths such as lherzolite, pyroxenite and wehrlite. The magmas erupted in the Big Pine volcanic field were generated by melting of lithospheric mantle that had been modified by subduction processes 1.8 billion years ago. Research conducted in 2008 suggested that the mixing and melting of two origin magmas is necessary to generate the observed rock compositions. After formation, the magmas at Big Pine quickly rose to the surface, preventing the formation of rhyolites which would require the magmas to stall within the crust. Owens Valley is windy and sunny with yearly temperatures fluctuating with strong diurnal temperature fluctuations. The Owens Valley lies in the rainshadow of the Sierra Nevada and thus the climate of the valley is dry with about precipitation. Vegetation in the valley is dominated by species adapted to arid and semiarid climates and includes Alkali sacaton, big sagebrush, greasewood, Nevada saltbush, rubber rabbitbrush, salt grass and shadscale.