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View of South Inyo Crater toward the north; the base of Deer Mountain is in upper left. The crater is about 200 m in diameter and 60 m deep. In the north wall of the crater, several layers of volcanic rock are exposed, including from bottom to top: (1) basalt lava flows that were erupted on the west side of the caldera; (2) andesite tephra about 10 m thick; (3) tephra erupted from the Inyo vents at South Deadman, Obsidian, and Glass Creek about 1 m thick; and (4) tephra erupted from the Inyo Craters and Deer Mountain crater, especially from the South Inyo Crater, about 13 m thick. In the photo, the section labeled Inyo tephra includes layers 3 and 4. The lava flows extend to a depth of about 300 m below the crater rim. Scientists have identified 26 different lava flows ranging in thickness from 1 to 26 m and 8 layers of volcanic deposits formed by explosive activity. This sequence of deposists was erupted between 200,000 and 100,000 years ago, well before the Mono-Inyo Craters volcanic chain became active. The andesitic tephra is older than about 64,000 years old. |
