One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 5 w7 m {! c1 k, Y4 J) n
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 公仔箱論壇3 }8 V1 l8 E) O
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.) G# G4 M% w9 ? M5 I
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, tvb now,tvbnow,bttvb" j& K- S/ d- I$ ?5 o0 F, D
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 1 F3 ?+ m% [" t; r. C
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
% w5 r3 }( e" g. C6 \& S. I& z" n3 jTVBNOW 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。They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.( c8 R: ^! c! Y; b
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$ M- G. r7 n: ^tvb now,tvbnow,bttvbMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 公仔箱論壇) c) P: D. |, i: X$ J! i. _' b
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas, J5 |1 r" p3 B* M
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
! N8 M V+ ^0 e2 b5 }6 Hwww1.tvboxnow.complume reached as high as 50,000 feet.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。4 e- |" h+ }' {5 P: `! }/ R
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 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。5 J1 o: J' N4 e/ s* Q' k8 k
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
6 M, L! C- H; ^/ a+ ]4 u公仔箱論壇years. The island’s jagged edges were created by massive avalanches.
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Augustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
, J: f6 d4 \, V$ B# S0 awww1.tvboxnow.comof Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet " O9 @' J; G! P1 s. f/ c
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
2 _3 I! \6 R6 G4 S/ K" ?the continental crust, creating magma that drives the volcanic eruptions
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6 T+ f/ n+ R' @. G" c! ~% X1 Jwww1.tvboxnow.comAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
+ z* ` g2 B. d: q8 Y7 owww1.tvboxnow.comin the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.+ y4 E% V: K( \7 y L
1 p; D& d1 ^9 i- L L5 ]+ 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。The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising % ]* p7 @0 I% [1 d- u$ M Q e
and cooling of the air above. In contrast, a dark gray cloud of ash near the ground is probably an avalanche of hot ash and rock known & _$ U8 K/ Z+ z0 ?
as a pyroclastic flow.
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/ J+ I$ n4 J8 d' X+ NThis photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:
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% q$ c. B5 C0 s5 V5 Z8 J3 ` * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
. ~- F/ a& A2 p `* p% Lwww1.tvboxnow.com * A shockwave from the eruption could have blown a hole in the cloud deck.www1.tvboxnow.com% X0 [2 X4 n' u+ F7 X6 a
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.4 b% S/ m, C, M# t
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* l- p; ]8 `+ ?: YTVBNOW 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。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。& B. S5 U9 D8 d: N/ z- \2 N) v
Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. tvb now,tvbnow,bttvb* C3 K- r4 z6 |8 X% h N2 W+ y
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 whentvb now,tvbnow,bttvb& ~6 P9 N% x2 J: O( L
the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.
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Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.
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0 b9 M2 e* y0 ktvb now,tvbnow,bttvbMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in# Q% m& [4 A. @, W
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 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。- c8 {9 ]. X" j9 M" n
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
- k: }* H9 m5 z% G* jwww1.tvboxnow.comthis picture are from forest fires ignited by lava.
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O B) N, w w& ytvb now,tvbnow,bttvbEtna is a stratovolcano located on the island of Sicily. It is one of the most studied volcanoes in the world and. at 500,000 years old, it may1 J1 P! [% B! ?9 F( w& f: w
also be the oldest-known active volcano.
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+ c G4 s) k& Rwww1.tvboxnow.comA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high / |* {6 }! l" F) i5 W q$ Y: k
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.
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) [5 }0 {$ g! QPopoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
" J" [( M, l$ vtvb now,tvbnow,bttvbThe second highest peak in Mexico at 17,800 feet, this glacier-covered stratovolcano has erupted at least 20 times in the last 500 years and has caused 公仔箱論壇9 J( s5 W: ~% `; N
multiple evacuations of the city. This eruption in 2001 was caught by astronauts on the International Space Station, near the end of a seven-year period 6 z* V. J; r& ^5 J; Q0 J( _
of frequent activity. The plume reached heights of around 30,000 feet.公仔箱論壇) Y- @, c: ]' t+ p; S6 v$ [, I
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。4 E( S1 |* t$ q

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- e8 H; A0 Z; X& B# t4 ]0 V2 zTVBNOW 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。This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 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。3 \5 d; L) y* q& Z4 s8 i, W7 T
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.www1.tvboxnow.com6 Y' t9 q, V F( _1 x
3 k$ e: a1 b/ Kwww1.tvboxnow.comChaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic % Y& {) H' J) ~. `8 F
flows and volcanic mudflows called lahars. The caldera is relatively small at less than two miles wide, and sits on the flank of the larger Michinmahuida volcano.
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This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra " E4 N8 U. R7 o: t3 W2 ] n
is a shield volcano, which are made mostly of previous lava flows and tend to be broad and gently sloping. The Galapagos are part of an island chain 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。. T' U, j$ l2 x1 H- Q
formed by a hot spot where a plume of hot mantle rises up and melts the base of the ocean crust. As the Pacific plate moves over the relatively tvb now,tvbnow,bttvb$ h, K8 G3 `. p6 G* a
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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p9 e9 Z8 w K8 `2 ^, @NASA’s Terra satellite snapped this image of Shiveluch volcano erupting on Russia’s Kamchatka peninsula at the edge of the Pacific Ring of Fire in 2004. www1.tvboxnow.com' I# d- ^2 m, g7 @" Z' m _$ d! s
A lava dome had been growing in the volcano’s crater, followed by intermittent eruptions that lasted weeks. Shiveluch is a 10,400-foot-high stratovolcano
, Z+ A! t- [$ K2 r! L+ `; M# mtvb now,tvbnow,bttvbthat is at least 60,000 years old and has been erupting fairly often for the past 10 years. Its dome has collapsed multiple times, most recently in 1964,
4 ?. ?- p7 V# Ecausing avalanches of debris into the crater. |