At 10:38 p.m. last night, Alaska’s Mt. Redoubt made its first of five eruptions, the last blowing at 4:31 a.m., sending a cloud of volcanic ash 60,000 feet above sea level, according to the National Weather Service.
At the end of January, Redoubt experienced a series of volcanic earthquakes and new steam vents, which prompted scientists at the Alaska Volcano Observatory (AVO), to warn that Redoubt would soon erupt. The last time the volcano blew was during a five-month period between 1989 and 1990. At that time, the volcanic ash choked up four engines of a KLM commercial airliner, nearly causing it to crash before landing safely in Anchorage. At the moment Federal Aviation Administration officials have not stopped flights into Anchorage, but some airlines have canceled flights into the state’s capitol.
Stratovolcanoes, which are common throughout the Cascade and Aleutian ranges, tend to erupt suddenly and violently. Where shield volcanoes—such as those found in Hawaii—have shallow-sloping sides and erupt in slow-moving streams and rivers of meandering lava, stratovolcanoes are steep and discharge like a pent-up sneeze that can, in extreme cases, tear down the entire side of a mountain. A recent example of this is the 1980 eruption of Mount St. Helens, which sent pyroclastic flows—fluidized rock fragments and gasses—moving 50 to 80 miles-per-hour down the mountain, and 520 million tons of ash into the air.
So far, Redoubt’s explosions aren’t so violent. But Alaskans should prepare for a dusting of fine gray ash on cars and houses as long as the volcano erupts. And if the mountain acts anything like she did 20 years ago, those eruptions could continue for several months.