Mount Rainier is a massive stratovolcano located 54 miles (87 km) southeast of Seattle. It is the most prominent mountain in the contiguous United States and the Cascade Volcanic Arc, with a summit elevation of 14,411 feet (4,392 m). Mt. Rainier is considered one of the most dangerous volcanoes in the world, and it is on the Decade Volcano list. Because of its large amount of glacial ice, Mt. Rainier could potentially produce massive lahars that would threaten the whole Puyallup River valley.