Alaska's Mount Redoubt volcano spews ash in this photograph taken on March 15, 2009. (Photo: Heather Bleick/Courtesy of the Alaska Volcano Observatory /U.S. Geological Survey/Reuters/Corbis)
A Restless Volcano Comes Alive
Alaska's Mount Redoubt continues shooting ash and steam into the atmosphere as the chance of stronger eruptions increases
Illustration: Jim McMahon
Scientists are keeping a close eye on Alaska's Mount Redoubt, one of the state's active volcanoes.
Last weekend, Redoubt rumbled and shot ash and steam into the air. It was the first activity at the volcano since a series of eruptions in late March and early April.
Those previous eruptions were explosive. They sent massive amounts of ash 18,000 feet into the atmosphere, which then rained down on surrounding cities and towns.
Since the last eruption on April 4, scientists have observed some lava on Redoubt's surface. The volcano has been in what scientists call a lava dome-building phase. Lava domes are created when thick lava bubbles to the surface, cools, and then hardens into rock. If a dome collapses, powerful and dangerous eruptions will likely occur.
One of the most dangerous effects of a dome collapse is what's known as a pyroclastic flow. Pyroclastic flows cause hot toxic gases and pieces of rock to rush down the side of a volcano. These flows move incredibly fast, usually more than 60 miles per hour, and are very dangerous.
A pyroclastic flow might not occur at Redoubt. But scientists in Alaska are still watching the volcano closely for any signs that the lava dome has collapsed.
"As the [lava] dome continues to grow, the possibility of there being a collapse of that dome or an explosion that removes that dome is increased," Dave Schneider of the Alaska Volcano Observatory told KTUU news in Anchorage.
The most immediate result of Redoubt's eruptions will be—and has been—volcanic ash.
Ash doesn't pose a great risk to Alaskans' health because it isn't toxic. But it can be problematic for people with respiratory ailments like asthma. Ash isn't harmful to the environment either. In fact, as ash breaks down and mixes with rainwater and sunlight, it forms highly fertile soil. This allows many things to grow in volcanic regions.
The closest city to Mount Redoubt is Anchorage, Alaska's largest city, located 110 miles to the east of the volcano. Anchorage has dealt with ash fall from previous eruptions.
Redoubt's eruptions have been rather unpredictable since they began in late March. Scientists don't expect that to change. They say that the next big eruption at Redoubt will happen suddenly—and it should happen soon.
The volcano's current cycle of eruptions began in late January with several volcanic earthquakes. This led to ash and steam eruptions that began on March 15. Its last major eruption began in December 1989 and continued for six months.
Mount Redoubt is one of more than 50 active volcanoes in Alaska. There are a total of 169 active volcanoes in the United States in states like Hawaii, California, Washington, Oregon, and Wyoming.
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