Mount Redoubt, or Redoubt Volcano, is an active stratovolcano in the largely volcanic Aleutian Range of the U.S. state of Alaska. Located in the Chigmit Mountains (a subrange of the Aleutians), the mountain is just west of Cook Inlet, in the Kenai Peninsula Borough about 180 km (110 mi) southwest of Anchorage. Mount Redoubt towers 9,000 feet (2,700 m) above the surrounding valleys to the north, south, and southeast in little over 5 miles (8 km); it is also the third highest within the range, with nearby Mount Torbert, at 11,413 feet, being the highest and Mount Spurr at 11,070 feet being the second highest.
Active for millennia, Mount Redoubt has erupted five times since 1900: in 1902, 1922, 1966, 1989 and 2009. The eruption in 1989 spewed volcanic ash to a height of 45,000 ft (14,000 m) and caught KLM Flight 867, a Boeing 747 aircraft, in its plume (the flight landed safely at Anchorage). The ash blanketed an area of about 7,700 sq mi (20,000 km2). The 1989 eruption is also notable for being the first ever volcanic eruption to be successfully predicted by the method of long-period seismic events developed by Swiss/American volcanologist Bernard Chouet. The Alaska Volcano Observatory currently rates Redoubt as Aviation Alert Level Green and Volcano Alert Level Advisory.