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.
Three Sisters Wilderness
Many types of landforms make up the wilderness area, but the most common are volcanic features, the most notable being the Cascades which are stratovolcanoes having formed around 1.6 million years ago. Numerous cinder cones have formed on their flanks as well as many lava flows that contain hundreds of lava tubes.
The Three Sisters Wilderness ranges in elevation from . The Three Sisters—North Sister at , Middle Sister at , and South Sister at — are found in the eastern portion of the Wilderness. Including Broken Top—just to the south at — there are 14 glaciers offering one of the best examples of the effects of glaciation in the Pacific Northwest. Collier Glacier, between North and Middle Sister, is the largest glacier in Oregon. The headwaters of the Wild and Scenic Whychus Creek (formerly Squaw Creek) emerge in the Wilderness.