As the Indonesian volcano explodes, scientists fear something far more catastrophic may be brewing

11/12/2010 20:53

From The Boston Globe

THE MERAPI volcano, currently exploding more forcefully every day in Indonesia, is located on the Sundra Arc, one of the planet’s most complex and dangerous geological areas. This is where two large plates of the earth’s crust, the Australian and Indian plates, are rapidly plunging down below the mini Burma plate to create the world’s deepest and most powerful earthquakes and the world’s largest and most dangerous volcanoes. Some scientists fear that something catastrophic may be brewing beneath the Sundra Arc.

The world’s three most deadly tectonic events in recorded history all occurred in this arc of volcanic islands that include Sumatra and Java. Tambora, the largest volcano ever recorded in human history, erupted in 1815. Records were not very good at the time, but at least 100,000 people died in the supervolcano. The eruption wafted thousands of tons of sulfur dioxide into the atmosphere, which coalesced with raindrops to form a veil of sulfuric acid that reflected sunlight back into space, leading the following year to “The Year Without a Summer.’’

The veil of sulfuric acid also caused the atmospheric sunsets so favored by the maritime painter William Turner. But the weather was so atrocious in the summer of 1816 that Mary Shelley and her husband holed up on the shores of Lake Geneva where she wrote her creepy classic, “Frankenstein.’’

In 1831, the world’s second largest recorded volcano blew 4 cubic miles of material off the top of Krakatoa Mountain and into the Indian Ocean, where it created a 150-foot high tsunami that killed 34,000 people. This disaster was more fully recorded because the telegraph had just been invented.

And then there was the tsunami that occurred the day after Christmas in 2004. It killed 150,000 people and left millions more homeless.

The present cycle of tectonic activity probably started right around that time in 2004 when the Indian plate thrust rapidly below the Burma plate, initiating one of the deepest and most powerful earthquakes ever recorded. The Indian plate then plunged deeper into the earth’s interior, where it melted and started to rise through several miles of sediment as magma.

The magma emerging out of Merapi is not liquid lava like what we see flowing out of Hawaiian volcanoes. This material is more like half-melted rock that is extruded out of the volcano like toothpaste being squeezed out of a tube. But the magma also contains gases under pressure that are causing the eruptions, rockfalls of flaming hot boulders, and pyroclastic flows: shock waves of heated gas and ash that on Nov. 5 engulfed an entire village in a “safe’’ area nine miles from the base of the volcano.

These pyroclastic flows of ash and hot gas are what seared people’s lungs on Pompeii. They can also travel unseen across half a mile of water to incinerate ships at sea as they did when Mount Pelee erupted off the island of Martinique in 1902.

But Merapi is not the only volcano now active on the Sundra Arc. Within the past few weeks there have been many more deep earthquakes and 20 other volcanoes have also become active. Indonesia is also home to the Lake Toba supervolcano, believed to be the largest explosive eruption to have occurred on our planet during the past 25 million years.

The Toba supervolcano occurred between 67,500 and 75,500 years ago. The eruption is believed to have only lasted about two weeks, but it ejected 670 cubic miles of material into the air and covered all of Southeast Asia under 6 inches of ash. Parts of India and Malaysia still lie under the remains of more than 20 feet of ash from the eruption. Toba also ejected 100,000 metric tons of sulfuric acid that cooled the northern latitudes of the earth by up to 15 degrees Celsius. Almost no plants and animals survived the volcanic winter in Southeast Asia, and the world’s human population was reduced by 60 percent. Humanity passed through a genetic bottleneck because of the catastrophe that is still evident in our DNA today.

The conditions that caused the Toba supervolcano were the three tectonic plates rapidly crashing into each other at the Sundra Arc. What concerns scientists now is that conditions could be the same now as they were then. If that is the case we should not be worried about the effects of the volcano on aviation, as we were after last summer’s Icelandic volcano, but we should be very worried about the effects of tsunamis in the Indian Ocean and ash clouds and a volcanic winter on humanity and the world’s climate.



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