Mount Rainier, or Mount Tahoma, as it is traditionally called, is a large active stratovolcano (also known as a composite volcano) in Pierce County, Washington located 54 miles southeast of Seattle. It towers over the Cascade Mountains as the most prominent mountain in the contiguous United States and Cascade Volcanic Arc at 14,411 feet It is the highest mountain in Washington and the Cascade Range.
The mountain and the surrounding area are protected within Mount Rainier National Park. With 25 major glaciers and 35 square miles of permanent snowfields and glaciers, Mount Rainier is the most heavily glaciated peak in the lower 48 states. The summit is topped by two volcanic craters, each over 1,000 feet in diameter with the larger east crater overlapping the west crater. Geothermal heat from the volcano keeps areas of both crater rims free of snow and ice, and has formed the world's largest volcanic glacier cave network within the ice-filled craters. A small crater lake about 130 by 30 feet in size and 16 feet deep, the highest in North America with a surface elevation of 14,203 feet occupies the lowest portion of the west crater below more than 100 feet of ice and is accessible only via the caves.
Mount Rainier has a topographic prominence of 13,211 feet greater than that of K2 (13,189 feet). On clear days it dominates the southeastern horizon in most of the Seattle-Tacoma-Bellevue metropolitan area to such an extent that residents sometimes refer to it simply as "the Mountain." On days of exceptional clarity, it can also be seen from as far away as Portland, Oregon, and Victoria, British Columbia.
The Carbon, Puyallup, Mowich, Nisqually, and Cowlitz Rivers begin at eponymous glaciers of Mount Rainier. The sources of the White River are Winthrop, Emmons, and Fryingpan Glaciers. The White, Carbon, and Mowich join the Puyallup River, which discharges into Commencement Bay at Tacoma; the Nisqually empties into Puget Sound east of Lacey; and the Cowlitz joins the Columbia River between Kelso and Longview.