June 25, 2009
Eyewitness to eruption
Astronauts on the International Space Station just happened to be above a volcano when it erupted, capturing some stunning photos of the initial blast punching a hole through the clouds.
The Daily Mail (U.K.) reports:
Sarychev Peak, one of the most active volcanoes in the world, had been sitting quietly in the Kuril Island chain near Japan for 20 years, when it suddenly sprang to life on June 12.
Fortuitously, the International Space Station was flying overhead at the time, and managed to capture this spectacular image of the ash-cloud tearing through the atmosphere, sending clouds scattering in its wake in a perfect circle.
The station, which orbits the earth from a height of 220 miles, makes nearly 16 orbits of our planet every 24 hours, and happened to be in the perfect spot to see the dramatic eruption.
The unique images have provided a wealth of new information about the eruption process, and volcanologists are now excitedly poring over the data.
Most unique is the mist-like 'roof' to the cloud, believed to be either steam or condensing water pushed ahead of the advancing cloud of ash. Known as a 'pileus cloud', it lasts just moments, making this a rare snapshot.
Also visible, far below on the hillside, is the thunderous pyroclastic flow of super-heated rock as it cascades down the mountainside ... Appearing at the start of an explosive eruption, they can travel at 130mph, meaning there's nearly no escape for anyone or anything caught in its path.
But the most stunning aspect of the picture is the effect on the clouds: As the ash column punches its way towards the top of the atmosphere, the shockwave causes the clouds to scatter.
An alternative theory, one which these pictures is helping to test, is that as the ash rises, the surrounding air is pushed down, where it warms, and the increased heat causes the clouds to evaporate.
[...]
The last explosive eruption from Sarychev happened in 1989, with eruptions in 1986, 1976, 1954, and 1946 also producing lava flows.
Ash from the eruptions has been recorded to reach more than 1,500miles from the volcano and commercial airline flights have been disrupted.
The height of the plume was measured at five miles high - a huge distance into the sky, although not enough to worry the astronauts peering down from above.
The space program has yielded unexpected discoveries over the years, serendipity often playing a part in the process. The odds against astronauts being in the perfect location to observe the instant the volcano erupted must be galactically high, and yet here we are, with high resolution photos of something never seen before.
Oh, sure, pyroclastic flows have been seen over the centuries, just not often by people who live to tell about it.
Vulcanologists must be giddy.
Posted by Mike Lief at June 25, 2009 08:01 AM
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Comments
And Al Gore would say it's global warming.......
Posted by: idunno at June 26, 2009 06:30 PM