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A long-dormant supervolcano in California still holds over 1000 cubic kilometres of semi-molten magma. The find suggests the supervolcano is not entirely extinct, but a major eruption remains extremely unlikely.
Long Valley Caldera in east California is 32 kilometres across and almost a kilometre deep. It marks the spot where, 760,000 years ago, a supervolcano spewed out over 1400 cubic kilometres of material in just six days. Clouds of super-hot ash and rocks blanketed the surrounding 50 …