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.
Lassen Peak
The Lassen volcanic center includes Brokeoff Volcano, Lassen's dacitic lava dome, and a number of small andesitic shield volcanoes found northeast of Lassen Peak. The Lassen dome field includes 30 dacitic lava domes such as Bumpass Mountain, Mount Helen, Ski Heil Peak, and Reading Peak; other major lava domes include Chaos Crags, Eagle Peak, Sunflower Flat, and Vulcans Castle. Nearby shield volcanoes include Prospect Peak and West Prospect Peak, and there are three cones close to Lassen Peak: Cinder Cone, Hat Mountain, and Raker Peak. The hydrothermal area inside the Lassen Peak volcanic center, with features located southeast and southwest of Lassen Peak, represents the largest geothermal area in the United States besides the one present at Yellowstone National Park.