[Vulkanen] The ring of fire #6: Waar diverse vulkanen puffen

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Op zaterdag 26 oktober 2013 22:08 schreef Frutsel het volgende:
Cool. Er was ergens een etna topic maar vindt hem ff niet op mobiel

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In the extreme northeast region of Russia is the Kamchatka Peninsula. Familiar to people who play the board game Risk, Kamchatka is a huge mass of land sticking out into the north Pacific, and sitting on the peninsula is a cluster of volcanoes, some of them among the most active on the planet.

The biggest of these is Klyuchevskaya Sopka, a monster stratovolcano towering over 4750 meters (15,500 feet) high. It’s also the most active, having been more-or-less erupting continuously since the late 1600s. It’s erupted a dozen times just since 2000!

On Oct. 20, 2013, the Landsat 8 Earth-observing satellite flew over Klyuchevskaya, capturing a tremendously long plume of ash as well as two separate lava flows moving down the volcano’s flanks:

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Op zondag 3 november 2013 12:41 schreef Frutsel het volgende:
vet! thx!
het gaat maar door daar, daar zijn een stuk of wat vulkanen constant aan het uitbarsten
WKN / Russische vulkaanuitbarstingen: Wereldwijde zorgen?

je mag het daar ook wel inzetten als je wilt en leuk vindt?

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Earthquakes deep below West Antarctica reveal an active volcano hidden beneath the massive ice sheet, researchers said today (Nov. 17) in a study published in the journal Nature Geoscience.

The discovery finally confirms long-held suspicions of volcanic activity concealed by the vast West Antarctic Ice Sheet. Several volcanoes poke up along the Antarctic coast and its offshore islands, such as Mount Erebus, but this is the first time anyone has caught magma in action far from the coast.

"This is really the golden age of discovery of the Antarctic continent," said Richard Aster, a co-author of the study and a seismologist at Colorado State University. "I think there's no question that there are more volcanic surprises beneath the ice."

The volcano was a lucky find. The research project, called POLENET, was intended to reveal the structure of Earth's mantle, the layer beneath the crust. In 2010, a team led by scientists from Washington University in St. Louis spent weeks slogging across the snow, pulling sleds laden with earthquake-monitoring equipment. [Images: Trek Across Antarctica]

Right place, right time

Two earthquake swarms struck beneath the researchers' feet in January 2010 and March 2011, near the Executive Committee Range in the Marie Byrd Land region of the continent. As the researchers later discovered, the tremors — called deep, long-period earthquakes (DLPs) — were nearly identical to DLPs detected under active volcanoes in Alaska and Washington. The swarms were 15 to 25 miles (25 to 40 kilometers) below the surface.

"It's an exciting story," said Amanda Lough, the study's lead author and a graduate student in seismology at Washington University in St. Louis. Though there were no signs of a blast, a 3,200-foot-tall (1,000 meters) bulge under the ice suggests the volcano had blasted out lava in the past, forming a budding peak.

"We can say with pretty high confidence that there wasn't an eruption while we were out there," Lough told LiveScience's OurAmazingPlanet. "We had people installing [seismometer] stations and flying airborne radar over the ice. But from the bed topography, we can see there is something building up beneath the ice."

Scientists think that underground magma and fluids pushing open new paths and fracturing rock cause deep, long-period earthquakes. Many active volcanoes in Alaska's Aleutian Islands have frequently produced these deep earthquake swarms without any signs of impending eruptions. However, researchers also monitor the tremors because a sudden uptick in shaking was seen before eruptions at Mount Spurr and Mount Redoubt in Alaska.

A volcanic flood

If the volcano in Antarctica did erupt, it would melt the bottom of the ice sheet immediately above the vent. Scientists aren't sure what would happen next. In Iceland, volcanic eruptions can melt glaciers, causing massive floods called jökulhlaups. But the ice above the Antarctic volcano is more than a half-mile (1 km) thick.

"How West Antarctic ice streams would react to an eruption a hundred or more kilometers [60 miles] inland from the grounding line is a yet-to-be-answered question," said Stefan Vogel, a glaciologist with Australian Antarctic Division who was not involved in the study. The grounding line is the spot where glaciers detach from rock and float on water.

"There is certainly a need for more research, both in mapping the distribution and monitoring the activity level of subglacial volcanic activity beneath ice sheets, as well as studying the impact of subglacial volcanic activity on the hydrological system of glaciers and ice sheets," Vogel said in an email interview.

It would take a super-eruption in the style of Yellowstone's ancient blowouts to completely melt the ice above the active volcano, Lough and her co-authors calculated. And if the volcano under the ice is similar to ones close by, such as Mount Sidley, there's no risk of a super-eruption. [Big Blasts: History's 10 Most Destructive Volcanoes]

Instead, the millions of gallons of meltwater might simply hasten the flow of the nearby MacAyeal Ice Stream toward the sea.

"People hear the word 'volcano' and get caught up in the idea that it will change the way the ice sheet works, but this stuff has been going on underneath the ice [for millions of years], and the ice sheet is in balance with it," Lough said. "Everyday magmatism isn't enough to cause major problems."

Hugh Corr, a glaciologist at the British Antarctic Survey who also discovered a buried Antarctic volcano, said an eruption could have a big effect, but it's difficult to quantify.

"The biggest effect on the West Antarctic Ice Sheet is still climate change — warming the ocean, melting the ice shelves. That's the most immediate risk, compared to if a volcano might go off," said Corr, who was not involved in the study.

A geologic puzzle

Signs of active and extinct volcanoes pop up all over Antarctica. Ash layers and lava indicate volcanoes spouted while the continent froze during the past 20 million years or more. (An 8,000-year-old ash layer sits above the newly found volcano, but it comes from Mount Waesche, a nearby peak.)

"The [West] coast of Antarctica is like a ring of fire," Corr said.

The earthquake swarms line up with older volcanoes in the Executive Committee Range, suggesting the volcanic activity there is slowly migrating south by 6 miles (9.6 km) every million years. This migration is perpendicular to the motion of Antarctica's tectonic plate, so a hotspot or mantle plume is not feeding the volcanoes, Lough said. (A mantle plume should make volcanoes that line up parallel to plate motion, like those of the Hawaiian Islands.)

The big mystery is figuring out why the volcano and its forerunners even exist. "Antarctica is certainly one of the most fascinating and enigmatic of all of Earth's continents," Aster said. [Video - Antarctica: Solving Geologic Mysteries]

Let's set the scene. Antarctica is split by an incredible mountain range. Imagine if Utah's spectacularly steep Wasatch Mountains cleaved North America from Texas all the way to Canada. That's what the Transantarctic Mountains are like. In the West, the land dives off into a deep rift valley, where the crust has been tearing apart for about 100 million years. The newly found volcano sits on the other side of this rift, in a higher-elevation region called Marie Byrd Land.

While the torn crust may seem like the best explanation for Antarctica's many volcanoes, many of the peaks fit no obvious pattern. Rifting and volcanism in Antarctica could be like nowhere else on Earth. "What is going on with the crust in Antarctica is still puzzling," Lough said.

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A newly discovered volcano rumbling beneath nearly a mile of ice in Antarctica will almost certainly erupt at some point in the future, according to a new study. Such an event could accelerate the flow of ice into the sea and push up the already rising global sea levels.

When the volcano will blow is unknown, "but it is quite likely" to happen, Amanda Lough, a graduate student in seismology at Washington University in St. Louis, Mo., told NBC News.

"At some point, it is going to erupt," she said. "Is it going to erupt in any of our lifetimes? That is not something that we can pinpoint."

And when it does erupt, she added, "there would be an increase in melting around the area. … You would add water to the system beneath the ice sheet … and that could cause that ice stream to speed up."

In other words, global warming likely isn't the only factor causing sea levels to rise, and the discovery of a subglacial volcano adds another layer of complexity for scientists trying to model how polar ice sheets move as the world gets warmer. But what overall impact this might have on global sea levels is unknown — and up for debate.

"The implication of large amounts of under-ice water accelerating ice flow, ice discharge and, thus, raising sea levels is 'permissible,' but remains highly speculative," Robert Bindschadler, an expert on glacial ice dynamics and emeritus NASA scientist now living in Quilcene, Wash., told NBC News in an email. "The actual processes involved are still very much topics of research."

Bindschadler was not involved in the new research, which Lough and colleagues discuss in a paper published Sunday in the journal Nature Geoscience.

Surprise discovery
Hints of the unnamed volcano's existence first appeared in seismic data collected by an array of instruments strung across the West Antarctic Ice Sheet. Lough's job was to analyze the data for earthquakes. "I found this grouping of events that kept being located at the same location over and over again," she said. "And when you see something like that, you want to go see what is causing it."

She typed the quakes' location into Google Earth to look for any features that could explain the shaking. She saw a group of nearby mountains, but ruled them out as the source since they were not an exact match. But as more and more earthquakes popped up in the seismic data, her team revisited the mountains.

"We realized they are actually a chain of volcanoes that date younger as they go south and the earthquakes were south of the volcanoes," Lough said. A subsequent examination of the bedrock topography made with airborne radar revealed a slight rise above the source of the weak, low-frequency quakes.

Intrigued, Lough shipped her seismic data off to a volcano seismologist who said the signature was consistent with a type of earthquake caused by magma coursing through the Earth's crust. Though these quakes could also be caused by the movement of glacial ice, they occurred between 15 and 25 miles beneath the surface of the ice, much too deep to be related to the pile of ice not quite one mile thick.

The final clue came from a distinct layer of ash dated to about 8,000 years ago in the vicinity of the earthquake cluster. At first, Lough said, she and her colleagues thought it was from an earlier eruption of the suspected volcano, though they later concluded it was more likely from Mount Waesche, a known existing nearby volcano that, in geological terms, erupted recently.

"All of the lines of evidence just fell together nicely," Lough said. The clusters of earthquakes "are indicative of magma movement in the crust and that this area is still quite active."

Eruption consequences uncertain
The earthquakes, Lough noted, are "not necessarily a precursor" to an imminent eruption. "Any volcano that is still not extinct, that still has an active magma chamber, is going to be showing seismicity whenever you have the magma moving around in the crust."

Given the nearly mile-thick pile of ice covering the volcano, any eruption anytime soon would unlikely vent to the surface, according to Lough. Rather, the heat from the eruption would melt the surrounding ice, which would lubricate the flow of the overlying ice sheet.

"All of these processes could lead to accelerating ice mass loss in West Antarctica," John Behrendt, a geophysicist at the University of Colorado's Institute of Arctic and Alpine Research, wrote in an accompanying article in Nature Geoscience.

Whether that will happen, Bindschadler noted, is debatable.

"In my opinion, it boils down to whether the excess water would flow under the ice as a sheet or within a more confined channel," he said, adding that sub-glacial water flow typically evolves from sheets to channels. "I think, in this volcanic case, the water would start local and form a channel to get to the ocean. This would produce a minimal change to the ice sheet dynamics."

Bindschadler cautioned, however, that this is just his "reading of the tea leaves."

So little is known about the bottom of the West Antarctic Ice Sheet that models of ice motion over it are unable to reliably predict what to expect from a subglacial eruption, noted Slawek Tulaczyk, a glaciologist at the University of California, Santa Cruz.

However, the new paper, he added in an email to NBC News sent from Antarctica, "serves as an important reminder that, in addition to climate changes, one-off events such as volcanic eruptions or subglacial lake floods may influence the rate at which Antarctica looses ice to the ocean."

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Indonesische vulkanen Sinabung en Merapi uitgebarsten

Foto In Indonesië zijn maandag de vulkanen Sinabung en Merapi uitgebarsten. Het vliegverkeer is gewaarschuwd en er worden voorbereidingen getroffen voor evacuaties.

De 2600 meter hoge Sinabung in Noord-Sumatra stootte maandag as uit tot een hoogte van achtduizend meter, zei vulkanoloog Surono. De vulkaan 'sliep' de afgelopen drie jaar, maar heeft sinds september sporadisch erupties. Het ministerie van verkeer heeft de luchtvaart gewaarschuwd uit de buurt te blijven van de vulkaan.

Ook de Merapi in Midden-Java was maandag actief. De aswolk hier kwam niet hoger dan tweeduizend meter. Ongeveer zeshonderd gezinnen zijn verzameld om eventueel geëvacueerd te wirden. Bij een uitbarsting van de Merapi eind 2010 kwamen meer dan driehonderd mensen om het leven en moesten twintigduizend omwonenden in veiligheid worden gebracht.
Bron: AD