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Super eruptions are disasters like none other
By Ned Rozell


May 31, 2007

Earth is pocked with giant craters that are reminders of a natural hazard that has happened before, and hopefully won't happen again any time soon-the "super eruption."

Stephen Self, a volcano researcher from Open University in England, was in Fairbanks recently to lecture on super eruptions. The last super eruption happened in 1815, when a tropical volcano named Tambora exploded for two days, leaving behind a giant caldera and pumping so much ash and sulfur dioxide into the atmosphere that 100,000 people died the year after the eruption. The ash and gases didn't kill them, but the volcano's affect on the atmosphere did. In many areas of Europe, crops failed to grow that year in the low light conditions.

Temperatures in London were 5-to-8 degrees Celsius cooler in 1816, Self said. "It was the 'Year Without a Summer' in the northeastern U.S., a year that inspired people to move West."

jpg 1912 eruption of Katmai

One of the closest events Alaska has experienced to what scientists call a "super eruption" is the 1912 eruption of Katmai, which turned 40 square miles of the world's best bear habitat into a sheet of ash.
Ned Rozell photo.

Super eruptions don't happen often, but they have been much larger than the Tambora eruption. An eruption in about AD 1452 was twice the size of Tambora, and both Long Valley Caldera (California) and Yellowstone (Wyoming and Idaho) are the earthly scars of super eruptions that affected large areas with their ashfall and lingering effects on the atmosphere.

"Yellowstone covered a large portion of the Lower 48," Self said. "If another of these should occur, an entire country could be covered by ash."

A super eruption could put the brakes on life as we know it, Self said. A big eruption would pump so much ash and particulates into the air that the whole planet would cool by as much as 10 degrees Celsius. Crops would fail and sulfur dioxide would eat holes in the ozone. Self said there is basically no way to prepare for a super eruption and it is perhaps foolish to worry about them, but how can a volcanologist not think of them?

jpg Katmai Caldera

View from the north rim of Katmai Caldera, a collapse feature that formed during the catastrophic eruption in June of 1912. Katmai Caldera is partially filled by a blue-green lake that is more than 800 feet deep.
Photo by R. McGimsey, U.S. Geological Survey,
courtesy of the Alaska Volcano Observatory and the U.S. Geological Survey.

"Even though they are very, very rare, I think it's worthwhile to go through the mind exercise of imagining what they might be like," Self said.

Steve McNutt of the Alaska Volcano Observatory in Fairbanks agreed with Self's assessment of a super eruption being bad for business when it comes to being human.

"If there were an entire season of crop failures worldwide, it would not be pleasant," McNutt said.

McNutt has studied the precursors of a super eruption. He's looked at earthquake swarms-numerous internal earthquakes that precede volcanic eruptions-to see if a longer period of swarms relates to a larger eruption. Included in his data set was information from the Katmai eruption of 1912, recorded by Japanese scientists who had deployed some of the world's first seismometers.

Katmai, which created the Valley of Ten Thousand Smokes on the Alaska Peninsula, was the largest eruption of the 20th century, and is one of the few eruptions in modern times large enough for McNutt to consider a super eruption. Looking at the earthquake swarm data for Katmai, McNutt noticed the volcano had several large earthquakes, as high as magnitude 5.5, before it erupted. That fit with other data that showed that super eruptions will provide warnings of their eminent debut through increased earthquake swarm activity. So, while we may not be able to do much about a super eruption, scientists may be able to see one coming.

"I think it's unlikely we'd be blindsided," McNutt said.



This column is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Ned Rozell [ ] is a science writer at the institute.


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