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EarthQuakes reactivate volcanoes in Chile
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and remember 1 of each 5 active volcanoes in the world are in Chile...
[link to www.dailygalaxy.com]
Could Volcanic Eruptions Follow Chile's Earthquake? Experts (& Recent History) Say "Yes"
According Oxford University volcanologist, David Pyle, Chile's magnitude 8.8 earthquake may be a prelude to a series of volcanic explosions. "We expect to see an upsurge in volcanic activity over the next 12 months," said Pyle.
In his notebooks of the voyage of the HMS Beagle, Charles Darwin noted the link between a large earthquake off Chile's coastline in February 1835 and previously inactive volcanoes: "The papers will have told you about the great Earthquake of the 20th of February. I suppose it certainly is the worst ever experienced in Chili (sic). It is no use attempting to describe the ruins--it is the most awful spectacle I ever beheld. The town of Concepcion is now nothing more than piles and lines of bricks, tiles and timbers-- it is absolutely true there is not one house left habitable."
Last year, Pyle and his colleagues found that after a magnitude 8.3 in 1906 and a magnitude 9.5 earthquake in 1960, there were three or four more volcanic eruptions within about 500 kilometers of the epicenter in the following year than would normally be expected.
Last week's earthquake occurred on the same section of fault that caused the earthquake Darwin observed in 1835. "We'll be using satellite measurements of heat and deformation to keep an eye on the entire arc of volcanoes, from Llaima in the south to Tupungatito in the north," said Pyle.
The image above shows a plume of ashes spewed by the Chaiten volcano as seen from the city of Chaiten, 1,200km south from Santiago, Chile on May 5, 2008 -its first activity in over 9,000 years.
The image below shows local residents being helped to board during evacuation operations following the eruption of the Chaiten volcano on May 2, 2008. About 1,500 people had to be evacuated after the eruption, which caused a red alert in neighboring regions of Chile and Argentina.
Pyle and Oxford University colleagues studied the massive Chaitén volcano that began to erupt explosively on 2 May 2008 -the biggest volcanic eruption in almost 20 years. The study showed that the impact of past eruptions is likely to have been significantly underestimated as much of the evidence quickly disappears, For six days afterwards the volcano pumped huge volumes of ash high into the atmosphere before its activity began to decline to a low intensity eruption
"The area around a volcano immediately after an eruption is like a crime scene where the evidence can quickly be destroyed by the elements,’ said Pyle of Oxford University’s Department of Earth Sciences. ‘Ash deposited on land will rapidly be removed by rain or wind, while ash deposited out to sea is only accessible by collecting core samples of the sea-floor sediment. This makes it extremely difficult for volcanologists to accurately reconstruct a past eruption from the available evidence and say how much fine ash was deposited, and over what area, during an eruption.’
The team’s work on Chaitén has shown that the several millimeters thickness of ash deposited across Argentina have been lost from wide areas – of at least 50,000 square kilometers – in only nine months.
‘By using satellite imagery to guide us, we were able to map the ash fallout across Argentina to a thickness of less than one tenth of a millimeter,’ said Sebastian Watt, a PhD student in Oxford’s Department of Earth Sciences, who led the team. ‘We collected samples from over 220 sites across an area of 100,000 square kilometres and with these field data and samples we were able to make the first scientific assessment of the size and impact of the eruption.’
The Chaitén eruption had immediate social and economic impacts across Patagonia (southern Chile and Argentina), with more than 5,000 people evacuated from settlements up to 75 km from the volcano, and extensive ash deposition leading to regional disruption of agriculture and aviation. The volcano was not routinely monitored, and there was no recognised warning before the eruption started.
The Andes Mountains along the western coastline of South America include numerous active steep-sided, cone-shaped stratovolcanoes. The majority of these volcanoes were formed and are still fed by magma generated as the Nazca tectonic plate under the southeastern Pacific Ocean moves northeastward and plunges beneath the South American continental plate—a process known as subduction. The Nazca plate is the source of last week's earthquake. The line of Andean volcanoes marks the approximate location of the subduction zone.
This astronaut photograph (below) highlights two volcanoes located near the southern boundary of the Nazca–South America subduction zone in southern Chile. Dominating the scene is the massive Minchinmávida Volcano (image upper right). Charles Darwin observed an eruption of this glaciated volcano during his Galapagos Islands voyage in 1834; the last recorded eruption took place the following year. When this photo was taken, the white, snow-covered summit of Minchinmávida was blanketed by gray ash erupted from its much smaller but now-active neighbor to the west, Chaitén Volcano.
Chaitén is dominated by a large lava dome within a caldera. With no recorded history of eruptions, Chaitén roared back to life unexpectedly on May 2, 2008. Volcanic activity continued at Chaitén in early 2009; several days before this astronaut photograph was taken, a new lava dome partially collapsed and generated a a scalding avalanche of gas, ash, and rock debris. A steam and ash plume extended northeast from the eruptive center of the volcano at the time of this image.
Casey Kazan via New Scientist and University of Oxford.
[link to www.boston.com]
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