Mount Redoubt, pictured in this photo essay in fall 2012, is a familiar peak darting from the horizon in Southcentral Alaska. And sometimes this volcano likes to rumble.
The 1989 eruption of Mount Redoubt wasn't exactly among the largest in Alaska during the 20th century -- the peak activity merited a Volcanic Explosivity Index rating of 3 on a scale of 1-7 -- but it was among the most disruptive and expensive. It's also fresh in many Alaskans' memories, as it occurred much closer to the state's largest city of Anchorage than those larger eruptions taking place in the Aleutians.
The eruption lasted from December 1989 until April 1990, with 23 major explosive events in that time. The multiple explosions rained ash over a good portion of the Cook Inlet region and Southcentral Alaska, and in its early stages seriously hindered air travel. A National Weather Service report estimates that the eruption cost about $160 million, making it the second costliest volcanic eruption in U.S. history, with only the massive Mount St. Helens eruption of 1980 costing more.
The eruption began on Dec. 14, 1989, when Mount Redoubt -- located about 100 miles southwest of Anchorage, across Cook Inlet -- spat an ash cloud into the sky following a day of intensifying seismic activity. The timing was particularly bad, with the busy holiday travel season just getting under way.
KLM flight 867, a Boeing 747 headed for Anchorage International Airport, flew through the ash cloud at an altitude of about 25,000 feet, which resulted in all four of the aircraft's engines dying. After plunging more than two miles to about 13,000 feet, the pilots were able to restart the engines and land safely at the airport. The cost of damages to the plane alone? About $80 million.
The AVO reports that "about 20 significant tephra deposits" resulted from the lengthy eruption, interrupting air travel numerous times and scattering ash on the Kenai Peninsula that led to more than 1,000 days in lost labor and three days of school closures.
Redoubt wasn't finished, either; in 2009, Redoubt erupted again, prompting flight cancellations and a slight ashfall in Anchorage.
--by Ben Anderson