Geyser
Yellowstone is the largest geyser locale, containing thousands of hot springs, and approximately 300 to 500 geysers. It is home to half of the world's total number of geysers in its nine geyser basins. It is located mostly in Wyoming, USA, with small portions in Montana and Idaho. Yellowstone includes the world's tallest active geyser (Steamboat Geyser in Norris Geyser Basin), as well as the renowned Old Faithful Geyser, Beehive Geyser, Giantess Geyser, Lion Geyser, Plume Geyser, Aurum Geyser, Castle Geyser, Sawmill Geyser, Grand Geyser, Oblong Geyser, Giant Geyser, Daisy Geyser, Grotto Geyser, the Fan & Mortar Geysers, & the Riverside Geyser, all in the Upper Geyser Basin which alone contains nearly 180 geysers.
Mount Meager massif
Volcanic activity of the third eruptive period occurred between 1,100,000 and 200,000 years ago. A thick sequence of andesite lava flows were erupted from the volcanic plug of Devastator Peak, creating the Pylon Assemblage. With a maximum thickness of more than , the Pylon Assemblage is the largest rock unit comprising the Mount Meager massif. The lava flows are layered, separated by a thin layer of lapilli tuff and reddened breccia. A concentration of subvolcanic intrusions and coarse volcanic breccia clasts more than in length suggest that Devastator Peak is a major vent.