HILO >> Astronomers working at the Keck Observatory on Mauna Kea have discovered what they call the "most energetic" volcanic eruption ever seen in the solar system. Big Isle provides view
to massive volcano in spaceBy Rod Thompson
rthompson@starbulletin.com
The eruption at Surt volcano on Jupiter's moon Io was large enough to cover Los Angeles, said Franck Marchis, one of the discoverers.
COURTESY PHOTO
A huge volcano on Io, one of Jupiter's moons, was observed over a period of days from Mauna Kea in February 2001.
"This eruption is truly massive," said Ashley Davies, a scientist at the NASA Jet Propulsion Laboratory who helped analyze the data.
The eruption took place in February 2001 on Io, one of the four large moons of Jupiter. Astronomers needed time to analyze the data and to publish their findings in the November issue of the planetary journal Icarus.
The discovery was made by postdoctoral researcher Marchis and astronomy professor Imke de Pater, both of the University of California at Berkeley.
Using an infrared camera and the Keck II telescope, the two took images of Io on Feb. 20, 2001. Two days later, a second image showed that a small hot spot had turned into a large, bright eruption.
A graphic illustration created by Marchis of the size of the eruption shows that magma spread out for a distance of about 15 miles in all directions, producing a blotch of lava about 30 miles across.
In comparison, the illustration shows, the whole of Mount Etna, Italy, could fit inside the blotch.
"The Surt eruption appears to cover an area of 1,900 square kilometers (734 square miles), which is larger than the city of Los Angeles," Marchis said.
But a better measure of the size is the amount of energy put out.
The amount of energy from Surt at any one time: 78,000 gigawatts, or 78,000 times a billion watts. In comparison, a 1992 eruption of Mount Etna put out only 12 gigawatts, and a 1983 eruption of Krafla volcano in Iceland put out 50 gigawatts.
"It is clear that this eruption is the most energetic ever seen, both on Io and on Earth," Marchis said.
What about famous earthly eruptions like Pinatubo in 1991, Mount St. Helens in 1980 or Krakatau (Krakatoa) in 1883?
Those were all explosive eruptions in which energy was released quickly and the event was over, Marchis said.
The Surt eruption is more like eruptions in Hawaii, which go on and on, so the total energy released is greater, he said.
The temperatures of lava from the two volcanic system are comparable, about 2,000 degrees Fahrenheit for Surt, just a bit hotter for Kilauea.
So which is bigger, Earth eruptions or Io eruptions?
At the Hawaiian Volcano Observatory, the size of eruptions is measured in volume of lava erupted, said observatory scientist Arnold Okamura. The energies of Surt and Etna were measured from space in gigawatts, so the two sets of numbers cannot be compared.
Enough lava to cover Los Angeles is really big, but other eruptions on earth have covered even more land, Okamura said.
The prehistoric Columbia River Basalts in Washington, Oregon and Idaho cover more than 60,000 square miles, and the "Deccan Traps" of India cover 200,000 square miles. But those took place millions of years ago and were not seen by humans.
W.M. Keck Observatory
