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Geologic map of the Sonoma Volcanics. The Sonoma Volcanics are a geologic formation of volcanic origin that is widespread in Napa and Sonoma counties, California.Most of the formation is Pliocene in age and includes obsidian, perlitic glass, diatomaceous mud, pyroclastic tuff, pumice, rhyolite tuffs, andesite breccias and interbedded volcanic lava flows.
[20]: 21–22 In the Long Valley region, where the craters are located, basin and range extension encroaches onto the thick and stable crust of the Sierra Nevada. [21] Geologic map of the area. Basement rock under the Mono–Inyo chain consists of the same granitic and metamorphic rock that make up the Sierra Nevada.
Before Obsidian Butte was emplaced and thus became available for obsidian production, people in the region used obsidian from the Coso volcanic field; [44] this trend away from Coso towards Obsidian Butte was recognized even before the exact timing of the Obsidian Butte eruption was known. [42] How the magmas are formed is controversial.
Obsidian has also been found in Gilat, a site in the western Negev in Israel. Eight obsidian artifacts dating to the Chalcolithic Age found at this site were traced to obsidian sources in Anatolia. Neutron activation analysis (NAA) on the obsidian found at this site helped to reveal trade routes and exchange networks previously unknown. [52]
In fact, the mountains are named for the numerous deposits of obsidian found on their slopes. [ 2 ] [ 8 ] [ 24 ] There is a wide variety of high-quality obsidian found in the area including jet black, brown, green, red fire, pumpkin, mahogany, midnight lace, rainbow, gold sheen, silver sheen, and snowflake as well as several double flow varieties.
Plant communities include California oak woodland, riparian woodland, Douglas fir forest, chaparral, grassland, and marsh. The dominant plant community is the oak woodland, which has a canopy of coast live oak, Garry oak, black oak, Pacific madrone, bigleaf maple, and California laurel. Canyon live oak occurs in swales and creeks.
A rarely seen deep sea fish resembling a serpent was found floating dead on the ocean surface off the San Diego coast and was brought ashore for study, marine experts said. The silvery, 12-foot ...
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