Sarah Rea November 17, 2018 June Lake, Lee Vining, Mammoth Lakes Obsidian Dome Sarah Rea November 17, 2018 June Lake, Lee Vining, Mammoth Lakes Obsidian Dome is a geology nerd’s dream. Nerd fact number one: The eruption date for the area around Obsidian Dome is one of the best estimated eruption dates in the prehistoric period on the planet.