One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic & F8 R( L" `, n' s- r0 @0 \6 F7 c
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
) a. c- B. m! C$ o6 C7 k) @7 T5.39.217.76active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
% L) W* S8 g5 J2 d; j" C& {; U2 WTVBNOW 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。Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
s. J3 E$ G* m% M4 A4 O公仔箱論壇erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 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。$ g/ B1 j9 f: i$ E+ F+ ]' k& [( j
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 4 s* @, d* x8 ?; M
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
2 Z: ~# A: u" b4 p9 \4 E8 dTVBNOW 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。( {/ u) W' m" C

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7 q: g2 K* q0 @8 LTVBNOW 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。Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 公仔箱論壇1 I& V; M& h/ x- _8 T* Y8 Z
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewasTVBNOW 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。: k8 ]& f, ^' R3 o% V$ e# x4 [
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
1 S5 B' ~5 J) g! x5.39.217.76plume reached as high as 50,000 feet.公仔箱論壇3 H0 q: P! {. D0 A
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; P, f, ~& ^: g* t* [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。Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
' z* C- F) r! k0 K) l5 m0 H. F# g% wsatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 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。/ T6 q; e% i$ V. C. |: ?1 Z
years. The island’s jagged edges were created by massive avalanches.5.39.217.760 O8 X3 W; R0 z, u
! h; T9 q2 G& h$ aAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring 公仔箱論壇8 j9 |# E! p" b* B! {" i y
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
' X8 B. W! T' z' Hocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
- t3 O4 t& C- V, Y( H+ B5.39.217.76the continental crust, creating magma that drives the volcanic eruptions5.39.217.76% e" _2 {% ^$ j7 o1 d; `
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: ~' ]2 J3 o& M$ v. oTVBNOW 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。
2 A0 v: s# i- a! r& r9 B5.39.217.76Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano 4 s+ K9 P8 A4 S+ K0 l5 V1 ^
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.
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The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising 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。; K& Z1 ^, m5 r' K& |6 W
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 5.39.217.76. q+ f+ l7 F/ @- S
as a pyroclastic flow.3 c- F6 n! b) F* j* W9 S
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This 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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' h7 ]& k0 x, _3 P& W5.39.217.76 * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.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。( J5 z U- ]0 o: s: F
* A shockwave from the eruption could have blown a hole in the cloud deck.8 {3 Y7 H1 T3 Y; d2 ]: h, l
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.3 J7 K5 k/ G& Q+ g u7 P( o7 D* i
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, |/ _. i, ~; C+ G: o+ Ttvb now,tvbnow,bttvbAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
" N& Y" Q) |9 O% ztvb now,tvbnow,bttvbIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
+ V" o( [& g' u; g% g4 P the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.tvb now,tvbnow,bttvb9 C* E( c/ z: R. u4 ^* y
* H7 m) _1 a( M7 z0 oTVBNOW 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。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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% T" b7 x7 I* \+ L: m DMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes inTVBNOW 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。$ I$ i. I( ^$ m* u+ ^
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
h8 d' t( T7 F' c; Ncaptured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in 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。; m, r7 |6 L) [8 z$ E. r
this picture are from forest fires ignited by lava.
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0 `4 F5 I8 w0 Q, C2 g: g8 l6 k+ {Etna 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 may) W; a y( ^3 d7 v( V }; s( ^
also be the oldest-known active volcano.5.39.217.760 D2 P* G) m1 ^1 l
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A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
* h. C1 y# M( X r1 d; [, T公仔箱論壇and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.tvb now,tvbnow,bttvb, s! ]; F" \+ w9 S. @8 b, N! S
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
3 ~0 U1 T7 u0 _9 I |The 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! ~; x |) b8 a d5 J' a1 B
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
! i( e1 _' K' a0 | g6 aof frequent activity. The plume reached heights of around 30,000 feet.5.39.217.76" b3 c5 v. ^7 m; @$ P- U. W6 c
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+ r& I" T6 @! C0 [5 C" y& C# UThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 5.39.217.76* t. d e! g {1 T. v2 Y0 F' R# k$ p
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.公仔箱論壇; E$ ]2 U3 C7 U
3 O" N9 T' A' ?% u# l7 [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。Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic 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 g7 _: g5 t K3 n7 o/ t7 \, o
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.tvb now,tvbnow,bttvb: s, k' N5 N2 w' D$ d2 A- @. `
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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
% _! Z7 N- ^7 ~3 X/ xis 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
6 g* E' M+ ` m- X6 O/ x6 cTVBNOW 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。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 0 f% W& V* F1 c8 Q
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.5.39.217.76$ j2 P \' T# m: p5 P' g4 A% ]9 U: J
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6 W% ^% N" X% H公仔箱論壇5.39.217.76* x& I* C' L( U& }
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. 5.39.217.768 _* a+ u/ C( d
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
; L! I" e' j/ B. t4 v9 nthat 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,
3 A4 r! \5 D; a' u8 MTVBNOW 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。causing avalanches of debris into the crater. |