Supervolcanoes with power to 'destroy civilisation' explode far more rapidly than scientists had believed - and one could be bubbling under U.S. right now5.39.217.76) o Z' j: d, i2 c; v3 B3 p
Most deadly event that can hit Earth short of asteroid
Scientists believed they took 100,000 years to build up
Instead, figure could be just hundreds
Supervolcano believed to be simmering under Yellowstone in U.S.
5 V: N$ D$ t0 {7 |A 'supervolcano' eruption is the most catastrophic natural disaster that can hit our planet, short of an asteroid impact - and now scientists believe they may build up a deadly head of steam far faster than we thought. / P9 N$ I: s8 H* f7 a% l/ M8 k& g
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Instead of the process taking hundreds of thousands of years, it could take just hundreds.; }0 F4 J9 x8 t+ q
- ^4 r- B' z9 N g0 X/ tThe news could be bad for the US, where a supervolcano is said to be simmering beneath Yellowstone National Park. If it erupted, two thirds of the country could be rendered uninhabitable. " Z& X# _& q, n' E+ H L5.39.217.76, P( q$ w! j" H Y( Y7 W) h" X" l; C9 n 0 e6 |+ \' r8 W6 k @9 R3 u公仔箱論壇Eruption: Supervolcanoes with the power to destroy human civilisations may build up a deadly head of steam far faster than scientists believed2 m8 p% X" C& D9 {1 {
Supervolcanoes are fuelled by giant pools of magma that form deep underground.tvb now,tvbnow,bttvb j$ B( }! e. i& g7 G! i0 L2 J
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Geologists had thought it took between 100,000 to 200,000 years for a supervolcano magma pool to build up enough pressure to erupt.tvb now,tvbnow,bttvb. w! \% _* Z) B! B% i& u6 |
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But the new study suggests that the giant magma bodies may only exist for a few thousand years, or even a few hundred, before exploding.tvb now,tvbnow,bttvb3 y+ k5 b, a$ ?( m& p" C
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A magma reservoir six miles below Yellowstone has been rising at a record rate since 2004. 4 D6 d9 Y* N& o9 {3 m公仔箱論壇) n- p. N+ v3 Q% `/ Z4 z1 i
The Wyoming park sits above a gigantic plume of hot and molten rock that begins at least 400 miles beneath Earth's surface and rises to 30 miles underground, where it widens to about 300 miles across.7 h: ?2 E7 t/ @" A
# z! Q0 ~" a# @2 [TVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。Blobs of magma occasionally break off from the top of the plume, and rise farther, resupplying the magma chamber beneath the Yellowstone Caldera. , F. o7 k3 E6 s- u5 H k6 u5.39.217.76 : j* P+ ^ `: t) J. S4 e5.39.217.76- G5 R7 [0 ]/ z$ J! y6 D
Steaming Mud Volcano at Yellowstone National Park in winter. Researchers now believe that the supervolcano beneath the park could be more active than thought 公仔箱論壇" k* X3 W( h* W
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The news could be bad for the US, where a supervolcano is said to be simmering beneath Yellowstone National Park. If it erupted, two thirds of the country could be rendered uninhabitable - v1 h9 q7 b: F0 e1 S3 iTVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。 , X V N) \" f7 r, ^: r' {6 G 公仔箱論壇( d K: n& S" A/ m" v }" }& n
Castle Geyser and sunrise Yellowstone National Park Wyoming: Researchers now believe that the huge 'supervolcano' beneath the park is far more active than previously thoughttvb now,tvbnow,bttvb5 D, l0 B% H) X P6 S
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Resembling the lid of a cooking pot, the caldera formed when the last super-eruption occurred 600,000 years ago.2 K8 w# b, Y* ^4 x
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" Q7 ~7 f5 N' ]6 o" @tvb now,tvbnow,bttvbThe supervolcano has erupted a total of three times in the last 2.1 million years. Scientists believe it could be due to erupt again. & f3 } x8 y' v0 h) jtvb now,tvbnow,bttvb4 S1 \0 J) c5 o6 ?9 T* |
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A full scale eruption at Yellowstone would be 1,000 times more powerful than the volcanic blast that tore apart Mount St Helens in 1980.5.39.217.76# L% `9 c+ p7 w: U: k+ R" r
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There is evidence that a similar super-eruption in Indonesia 74,000 years ago came close to wiping out the entire human species. & I; K4 @$ m6 M公仔箱論壇5 A& Y {, y' @
. q0 I6 k3 H, A' V! m! j Htvb now,tvbnow,bttvbThe new study was based on analysis of a super-eruption that occurred in eastern California 760,000 years ago.. h3 H/ _3 V8 M" E& Q8 P0 c
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Several independent lines of evidence indicated that the magma pool erupted within a few thousand years, perhaps within a few hundred years, covering half the North American continent with smouldering ash.tvb now,tvbnow,bttvb: S% H* Y1 Z# k9 V; E% f% V. e
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The scientists based their estimate on quartz crystallisation rates. Previous studies have relied on the growth of zircon crystals, which is said to be a less accurate method.tvb now,tvbnow,bttvb' y' ~, s: d5 a; H
! x2 |) H B' v4 O: d5.39.217.76 ) L2 ^! \9 N. d( s: e. ltvb now,tvbnow,bttvbThe research is published in the online journal Public Library of Science ONE. & ]- K4 T. E5 z' P9 d: z; T; U # @) a/ E7 K4 H* Y% s% w8 _5.39.217.76 2 g. @: H l9 x& `( O, b5.39.217.76Lead scientist Dr Guilherme Gualda, from Vanderbilt University in Nashville, Tennessee, said: ‘Our study suggests that when these exceptionally large magma pools form they are ephemeral and cannot exist very long without erupting.TVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。& A$ T+ ]7 _/ r! J/ e! z
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‘The fact that the process of magma body formation occurs in historical time, instead of geological time, completely changes the nature of the problem.’tvb now,tvbnow,bttvb1 V5 W( l4 ~/ }' R1 p. P
1 R# k% Z9 L2 l) k/ V/ Ttvb now,tvbnow,bttvb . ~/ {' U! l+ }. Itvb now,tvbnow,bttvbHe said regions such as Yellowstone should be monitored regularly to provide advance warning of a catastrophic super-eruption.作者: cms 時間: 2012-6-1 08:11 PM
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