Mount Rainier (), also known as Tahoma or Tacoma, is a large active stratovolcano in the Cascade Range of the Pacific Northwest, located in Mount Rainier National Park about 59 miles (95 km) south-southeast of Seattle. With a summit elevation of 14,411 ft (4,392 m), it is the highest mountain in the U.S. state of Washington and the Cascade Range, the most topographically prominent mountain in the contiguous United States, and the tallest in the Cascade Volcanic Arc.
Due to its high probability of eruption in the near future, Mt. Rainier is considered one of the most dangerous volcanoes in the world, and it is on the Decade Volcano list. The large amount of glacial ice means that Mt. Rainier could produce massive lahars which could threaten the entire Puyallup River valley. According to the United States Geological Survey, "about 80,000 people and their homes are at risk in Mount Rainier’s lahar-hazard zones."