Wednesday, October 04, 2006

The Butterfly Effect

This is an interesting example of the Butterfly Effect of Chaos theory.

In June 1912, Novarupta—one of a chain of volcanoes on the Alaska Peninsula—erupted in what turned out to be the largest blast of the twentieth century.

It was so powerful that it drained magma from under another volcano, Mount Katmai, six miles east, causing the summit of Katmai to collapse to form a caldera half a mile deep. Novarupta also expelled three cubic miles of magma and ash into the air, which fell to cover an area of 3,000 square miles more than a foot deep.

But the NASA GISS climate model showed that aerosols from an arctic eruption such as Novarupta tend to stay north of 30ºN—that is, no further south than the continental United States or Europe. Indeed, they would mix with the rest of Earth's atmosphere only very slowly.

This bottling up of Novarupta's aerosols in the north would make itself felt, strangely enough, in India. According to the computer model, the Novarupta blast would have weakened India's summer monsoon, producing "an abnormally warm and dry summer over northern India," says Robock.

Why India? Cooling of the northern hemisphere by Novarupta would set in motion a chain of events involving land and sea surface temperatures, the flow of air over the Himalayan mountains and, finally, clouds and rain over India. It's devilishly complex, which is why supercomputers are needed to do the calculations.

To check the results, Robock and colleagues are examining weather and river flow data from Asia, India, and Africa in 1913, the year after Novarupta. They are also investigating the consequences of other high-latitude eruptions in the last few centuries.

And if the Novarupta volcano affected India what did the Tunguska explosion in Russia in 1908 affect?

On June 30, 1908 a mysterious explosion occurs near Tunguska in Siberia, flattening a huge region and knocking down millions of trees. No meteorite remains are found in the area and the cause is never determined. Later speculation about possible causes ranges from an impact with a comet to an impact with a small black hole, although the most common explanation is a bolide (any sort of space object causing a fireball) that explodes high in the atmosphere.

But what if it wasn't a meteorite or space object but actually a terrestrial phenomena? Tunguska event of 1908 had to be of geophysical origin!



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