fron : http://spectregroup.wordpress.com/2010/04/22/acts-of-god/
No Fly Zone
“The year of the earthquake has suddenly become the year of the volcano. It raises the question of what governments can do to prepare for — and adapt to — wild-card geological events that not only affect airliners but can also alter the planet’s climate for years at a stretch. Now airports are beginning to open again in Britain and the Netherlands, but no one can be entirely sure what will happen next in Iceland. Eyjafjallajokull could incite an eruption of its larger neighbor, Katla, which hasn’t erupted since 1918 and might be ready to rumble. In all three historically recorded eruptions of Eyjafjallajokull — in 920, 1612 and 1821 — Katla erupted soon thereafter.”
“Each time Eyjafjallajokull has erupted in the past 2,000 years, Katla has exploded within six months. Professor McGuire pointed out that Katla was 10 times bigger than Eyjafjallajokull. It also has a much bigger ice cap, and it is the mixture of melting cold water and lava that causes explosions and for ash to shoot to high altitudes. Iceland’s President, Olafur Grimsson, indicated that Europe, and the world, would have to wake up to the risk posed by Katla. “Because the history of these volcanoes in my country shows that they will erupt regularly, and the time for Katla to erupt is coming close. I don’t say if, but when Katla will erupt, because it usually erupts every century and the last [major] one was in 1918.” The President said Iceland had been “waiting for that eruption” for some years, and had made preparations for rescue and emergency services. So I think it is high time for European governments and airline authorities to start planning for it.”
photograph by Marco Fulle
Volcanic Explosivity Index
“The map is almost uncannily similar to today’s: a spray of black dots showing the recorded sightings of a foul grey haze spreading across Europe – and all of it caused by clouds of ash from an immense volcano erupting far across the sea in Iceland. But this was a map made from data collected in 1783. The volcano was called Laki, it erupted for eight dismal months without cease, ruined crops, lowered temperatures and drastically altered the weather. It killed 9,000 people, drenched the European forests in acid rain, caused skin lesions in children and the deaths of millions of cattle. And, by one account, it was a contributing factor (because of the hunger-inducing famines) to the outbreak six years later of the French revolution.
It is worth remembering that ours is a world essentially made from and by volcanoes. There is perhaps no better recent example of the havoc that a big eruption can cause than that which followed the explosive destruction of Mt Toba, in northern Sumatra, some 72,000 years ago (which, in geological time, is very recent). The relics of this mountain today are no more than a very large and beautiful lake, 60 miles long and half a mile deep – the caldera that was left behind by what is by most reckonings the largest volcanic explosion known to have occurred on the planet in the last 25 million years. On the widely used volcanic explosivity index (VEI), Toba is thought to have been an eight (Eyjafjallajökull is by contrast listed as having a probable VEI rating of just two). About 680 cubic miles of rock were instantly vaporised, all of which was hurled scores of thousands of feet into the air. This this is what did the lasting damage, just as Iceland’s high-altitude rock-dust is doing today. But while we today are merely suffering a large number of inconvenienced people and a weakening of the balance sheets of some airlines, the effect on the post-Toban world was catastrophic: as a result of the thick ash clouds the world’s ambient temperature plummeted, perhaps by as much as 5C – and the cooling and the howling wave of deforestation and deaths of billions of animals and plants caused a sudden culling of the human population of the time, reducing it to maybe as few as 5,000 people, perhaps 1,000 breeding pairs.
Others of the 47 known VEI-8 volcanoes are more alarmingly recent. The newer of the great eruptions that helped form the mountains of today’s Yellowstone national park in Wyoming took place just 640,000 years ago, and all the current signs – such phenomena as the rhythmic slow rising and falling of the bed of the Yellowstone river, as if some giant creature is breathing far below – suggest another eruption is coming soon. When it does, it will be an American Armageddon: all of the north and west of the continent, from Vancouver to Oklahoma City, will be rendered uninhabitable, buried under scores of feet of ash. (I mentioned this once in a talk to a group of lunching ladies in Kansas City, soothing their apparent disquiet by adding that by “soon” I was speaking in geologic time, and that meant about 250,000 years, by which time all humankind would be extinct. A woman in the front row exploded with incredulous rage: “What? Even Americans will be extinct?”) Krakatoa’s immediate aftermath was dominated initially by dramatic physical effects – a series of tsunamis, a bang of detonation that was clearly heard (like naval gunfire, said the local police officer) 3,000 miles away, and a year’s worth of awe-inspiring evening beauty – astonishing sunsets of purple and passionfruit and salmon that had artists all around the world trying desperately to capture what they managed to see in the fleeting moments before dark…”