May 8, 2008

Chaiten’s Eruption Causes Emergency Evacuation

Southern Chile's Chaiten volcano has blanketed the entire area in a white cloud of ash that has reached as far away as Argentina.  Experts say the surprise eruption of the long dormant 3,280-foot Chaiten volcano, now in its seventh day, shows no signs of letting up and could go on for months.

The ash has left some animals dead, disrupted flights from Argentina to the southern Patagonia region and caused the waters of a fjord that Chaiten sits on and a river to now appear white.

The volcano is one of 200 to 300 volcanoes in the "Andean Arc" region of Chile, Peru, Ecuador and Columbia.  Volcanologists consider the area, some of which lie in much more densely populated areas, to be active, said a University of Colorado at Boulder geologist who has studied Chaiten.  However, only a few dozen of these active volcanoes are monitored.

While the public perception is that volcanoes that have not erupted in historic times are dormant, volcanologists consider any volcanoes that erupted during the last 10,000 years, which would include Chaiten, to be potentially active, said University of Colorado at Boulder geological sciences Professor Charles Stern.

Stern said the pyroclastic flow and ash-fall deposits he and Chilean colleagues analyzed in 2004 indicate Chaiten last erupted about 9,370 years ago. "We consider the lifespan of Andean volcanoes to be about 1 million years, which is supported by this new eruption," he said.

Chaiten, which started erupting on Friday and "ramped up significantly" Wednesday, could bury the nearby town of Chaiten much like the Roman city of Pompeii was buried by tephra, or volcanic material, following the eruption of Mount Vesuvius in 79 A.D., Stern said.

"There are 25 million to 30 million people that live very close to at least one of these potentially active volcanoes in the Andean Arc, including the cities of Quito and Santiago," said Stern. "This is a good example of what could happen at any time in the region, and it is fortunate the Chaiten eruption is occurring in a pretty sparsely populated area."

Chilean officials are hoping the eruption will ease, and are working to evacuate residents in the affected areas.

"According to experts, the (ash cloud) is less dense, which could indicate a lower probability of it exploding more intensely, but it's just a hypothesis," Sergio Galilea, Chile's top government official in the southern lake region, told Reuters during a flight over the erupting volcano.

The volcano has forced the evacuation of everyone within a 30-mile radius, including more than 4,500 residents of Chaiten, a village six miles away where a 6-inch coating of ash had contaminated ground water supplies. The navy evacuated people aboard its warships as the village can now only be reached by air or by boat. Those who were evacuated had to leave their pets and belongings behind.

Given the scope of the catastrophe, Chile's government did not rule out a permanent relocation of Chaiten's residents.   Chilean President Michelle Bachelet said it was the first time that nation has had to evacuate entire towns.   

"Everything is so uncertain," said Patricio Ide, 40, who was evacuated from Chaiten to Puerto Montt, 125 miles away from the eruption.

"This could last a month, three months, maybe we can never return. We are so worried," he said tearfully.    

Following a spike in activity on Tuesday, when the volcano spewed hot rocks and lava and a surging column of ash, officials said its two craters had fused and pressure had eased.  Nevertheless, the eruption continued, and experts said it would be weeks and possibly even months before residents could return.

Veterinarians went to Chaiten Wednesday to rescue hungry, thirsty and scared pets, bringing some of them back to Puerto Montt.

Evacuee Maria Angelica Hermosilla said she would go back the first chance she got. "There is nothing like Chaiten," the 42-year-old said. "Everyone knows each other, we are like a big family, there is no violence, no muggings."

Chaiten is huddled near a fjord 760 miles south of Santiago, and is a draw for adventure tourism, fishing and trekking.  Patagonia, a sparsely populated area at the southernmost tip of Latin America, cuts across both Chile and Argentina.  The region is known for its majestic snow-capped mountains, which include fjords, glaciers and volcanoes.

Rodrigo Rojas, an official with the National Emergency Office, said winds were pushing the cloud of ash into Argentina, but it no longer rose miles into the air as it did Friday when the eruption began.

Further east, remaining residents of Futaleufu were evacuated Wednesday.  But government geologist Luis Lara told Reuters he did not expect a catastrophic collapse of the volcano.  He said that any lava flow would not reach the town, but that a cloud of extremely hot and dense material could coat the surrounding area.

"The activity could continue for quite some time," he said. "It could be weeks, months. It could even be years, but not with the same characteristics -- with ups and downs."

One of the worst affected on the Argentine side of the border was the town of Esquel, where schools reopened after the flurry of ash finally ceased on Wednesday.   But officials have advised residents to refrain from drinking water from mountain streams, a common practice in the region, and to wear facemasks.  

University of Colorado's Stern said the possibility of the Chaiten volcano affecting Earth's climate is probably fairly low.

"In to order to significantly affect the climate, a volcano has to put out a lot of sulfur dioxide aerosols into the stratosphere for an extended period, which then reflects sunlight away from the Earth," he said.

"Our data from Chaiten showed the last eruption was high in silica and low in sulfur."

In contrast, the massive eruption of Mount Pinatubo in the Philippines in 1991 cooled the global climate for about one year because of high sulfur dioxide emissions, he said. The eruption of Tambora in Indonesia in 1815 affected the world's climate for about three years and caused what is known as the Year Without a Summer in 1816 by cooling Europe and North America with huge atmospheric sulfur dioxide emissions.


Image Caption: Chile's Chaiten Volcano is shown spewing ash and smoke into the air for hundreds of km over Argentina's Patagonia Plateau in this Envisat's Medium Resolution Imaging Spectrometer (MERIS) image, acquired on 5 May 2008. Credits: ESA


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