Alaska Volcanoes | Universe Today

Written by Jerry Coffey

Currently there are about 800 active volcanoes in the world. There are 40 active Alaska volcanoes. If you want to include volcanic fields the number increases to 130. All of them are said to have been active within the last 2 million years. 90 of them are believed to have been active within the last 10,000 years, while at least 50 of these have shown activity since 1760. Alaska volcanoes make up 75% of volcanoes in the US that have erupted within the last 200 years. This is understandable, because they are located along the Pacific Ring of Fire. Most Alaska volcanoes are specifically found in the Aleutian Arc, a chain of about 300 volcanic islands in the Northern Pacific Ocean.

Eruptions of Alaska volcanoes are typically very immense. A number of them have made it to the record books. Mount Redoubt's series of eruptions from 1989 to 1990 is the second most costly in US history, crippling the aviation and oil industries during that period. On December 15, 1989, for example, a Boeing 747 carrying 231 passengers sucked in volcanic ash from Mt. Redoubt Volcano. As a result, all four engines conked out and the plane dropped by about 3,000 meters. Luckily, the crew managed to bring the engines back to life. That single eruption cost $80 million.

One of the greatest eruptions in history was the 1912 eruption of Alaska volcanoes in what is now known as Katmai National Park and Preserve. The explosions lasted two days and sent about seven cubic miles of ash and pumice into the air. The wind blew the volcanic ash more than 100 miles away, to the town of Kodiak. Up to 25 cm of ash caused serious problems in Kodiak. It damaged buildings, cars and airplanes and polluted the water supply. Smaller ash falls reached as far as Puget Sound, 2,415 km away. Volcanic material also filled a glacier-carved valley and formed what is known today as the Valley of Ten Thousand Smokes. For more than 50 years, scientists believed Mount Katmai was the source of the eruption, but they later found that almost all of the magma that erupted came from the nearby Novarupta volcano.

Three Alaska volcanoes require a close eye: Augustine, Spurr and Redoubt. The Augustine volcano has been the most active volcano in the Cook Inlet region, erupting at least twice in the 1800s and four times in the last 100 years. An eruption in 1883 sent a tsunami slamming toward the small fishing village of English Bay. The 30-foot wave destroyed boats and buildings, but no one was killed. In 1986, ash blew out of the volcano, as well as giant white clouds of steam. Ash fell over the entire Kenai Peninsula and other areas, including Anchorage. The irregular coastline of Augustine Island is due to the repeated catastrophic collapse of the summit dome, forming debris avalanches down the flanks and into Cook Inlet.

Mount Spurr is a Quaternary stratovolcano located near the northeastern end of the Aleutian volcanic arc. It is the easternmost historically active volcano in the Aleutian arc and is the highest of several snow- and ice-covered peaks that appear to define a large, dissected stratovolcano. On June 27, 1992, Mount Spurr burst into eruption, shooting a mushroom cloud thousands of feet into the air. The ash cloud traveled over Cook Inlet into Anchorage, about 80 miles away. No lava came out of the volcano. It erupted again in July, August and September, blanketing Anchorage with more ash. It took several months to clean up all the ash. Prior to these eruptions, the volcano had been quiet for nearly 39 years.

As the most active of the Alaska volcanoes, Mount Redoubt's 1989-1990 eruption proved very damaging. Volcanic ash caused severe damage to aircraft and left some businesses and homes in Anchorage without power. The ash cloud was so thick, it turned daylight into darkness. Some schools even had to close. The explosion sent ash avalanches down a nearby glacier. The ash flows and floods from the melting glacier slowed oil production in Cook Inlet for several weeks. It was Redoubt's fourth and most damaging eruption of this century. The volcano also erupted in 1902, 1966 and 1967-68.

The Alaska volcanoes cause so much trouble that the Alaska Volcano Observatory was built. Scientists at the observatory in Anchorage keep track of the many volcanoes in Alaska. They gather information day and night about volcanoes from seismograph machines that let them know when the Earth is rumbling. Since volcanoes often make a lot of noise before they blow, scientists are able to warn us ahead of time of possible eruptions. The Alaska Volcano Observatory uses a color code to let people know how dangerous the eruption may be. Still, scientists are not 100 percent sure how powerful an eruption may be.

To get a lot of information about Mt. Redoubt, you should follow this link. Here on Universe Today we have a great article about the most active of Alaska volcanoes. Astronomy Cast offers a good episode about the plate tectonics that influence volcano eruptions.

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