| The widely famed Obsidian Cliff, extending half a mile and rising 150 to 200 feet above Obsidian Creek, which flows at its base, is situated about eleven miles south of the Mammoth Hot Springs at an elevation of 7,500 feet above the sea. Its upper half is a vertical face of black obsidian, or volcanic glass, which has resulted from the rapid cooling of a perfectly fused igneous rock, and the lower portion is a talus slope of the same material. (Iddings) |
