Yellowstone Geology Hayden Obsidian Cliff Legacyby Daniel J. Smith Black Gold: The Obsidian Cliff Legacy Yellowstone, Obsidian, Archaeology Yellowstone Volcano Observatoryby TIY Staff Yellowstone Caldera: Yellowstone Volcano Observatory Geology, Glaciers, Volcanism Climate ChroniclesMar o5 2017 by Daniel J. Smith Climate Chronicles: Local Evidence Climate Change, Geology, Glaciers