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Clear Lake volcan

Clear Lake champ volcanique se situe dans le nord de Coast Ranges, en Californie, ca. 135 km au nord de San Francisco. Le champ volcanique constitué de complexes dôme de lave, des cônes de scories et des maars du basaltiques à rhyolitiques-composition. Mont Konocti, un dôme de lave dacitique sur la rive sud du lac Clear, est le plus grand édifice volcanique.
La région a une intense activité gethermal, causée par une grande chambre magmatique est encore chaud silicique environ 14 km de large et 7 km sous la surface. Il fournit la source de chaleur pour les geysers, le plus grand du monde champ géothermique produisant sur le côté sud-ouest du champ volcanique. Ses centrales géothermiques peut générer environ 2000 mégawatts, soit suffisamment pour alimenter deux villes de la taille de San Francisco.
La dernière activité volcanique qui s'est passé il ya 10.000 ans et a formé maars et de cônes de cendres le long des rives du lac Clear, le lac d'eau douce naturelle Grandes, en Californie. Volcanisme autour du lac Clear est lié à la complexité du système faille de San Andreas transformer.

Introduction:

Volcanic activity has been largely non-explosive, with the exception of one major explosive eruption that must have occurred and deposited a airfall tuff. Most lavas found here range from basalt through rhyolite in composition, dacite being the most dominant type.

Eruptions at Clear Lake volcanic field:
4 eruptive episodes separated by time gaps of ca. 150-200,000 years have been recognized: 2.1-1.3 million years ago (m.y.), 1.1-0.8 m.y., 0.65-0.30 m.y., and 100,000-10,000 years ago. The total volume of about 100 individual eruptions exceeds 70 cubic kilometers.
Eruptive products from the first activity episode are found in the east of the field. The second activity episode constructed Cobb Mountain (1 million years, Ma) and Mount Hannah (0.9 Ma). The third episode of activity was at the Mount Konocti–Thurston Lake area, the most voluminous dacite and rhyolite feature of the Clear Lake volcanics.
The most recent activity, up to about 10,000 years ago were small mostly basaltic and andesitic eruptions in the north of the field.

Sources: GVP, NCGS (Northern California Geological Society)

Clear Lake Photos:

Vue claire sur le lac de lave dans le Marum (cratère ouest). (Photo: Tom Pfeiffer)	Again the Nyiragongo lava lake. The red glow of the lava was clearly visible through the day. (Photo: shinkov)	The sun is just about to rise above the horizon. The lava lake is mostly crusted over and the dry weather makes for a very clear view onto the lake. (Photo: Tom Pfeiffer)
Thanks to the risen level of the lake, the rim near the campsite now offers unobstructed, perfect views of the whole lake. And thanks to the prevailing easterly winds, it...	Exceptionally clear view onto a lava bubble from the lava lake inside Marum crater, Ambrym Island, Vanuatu (May 2012) (Photo: Thorsten Boeckel / www.tboeckel.de)	Clear view onto the western half of the lava lake from campsite. (Photo: Tom Pfeiffer)

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