One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 7 W, Y9 @4 P: e' h0 b
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are tvb now,tvbnow,bttvb& G1 p1 Q: Z; h6 W; b1 O! ~$ I. c
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
/ }+ u, |" h [7 K% U0 ~公仔箱論壇Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 公仔箱論壇# f f) U* ] K4 h6 T
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
' n) K+ @# N( `and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
3 I! N* F& B8 S; M( P" D3 Z' A公仔箱論壇They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.% Q( J+ x7 K3 D$ E9 P3 z \
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 5.39.217.76! G: m4 r9 a% U; m+ o1 Z- }
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
" w* P% ?7 y. w6 E! s& [tvb now,tvbnow,bttvbtaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash 5.39.217.767 n; F1 W/ V* b( P5 \
plume 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。/ N" P1 }' A$ s* |( j
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
9 i. x, o5 g; `4 Q5.39.217.76satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
- w- d2 c+ a( [' ~8 L4 u4 l+ Stvb now,tvbnow,bttvbyears. The island’s jagged edges were created by massive avalanches.
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( o [, [6 B! h; [+ ]1 l: j* T" sAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
0 d, j! l- W; j1 l# {4 m5.39.217.76of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet tvb now,tvbnow,bttvb+ ~! {9 [1 p) r7 ~) S
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of 5.39.217.76) K% _1 f3 T) S' i; \$ R
the continental crust, creating magma that drives the volcanic eruptions
5 e5 ~. I7 \7 e" J公仔箱論壇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。* q. l. Q7 ]6 @4 |6 L

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* t+ r4 p" P: q7 C8 kTVBNOW 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。Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano tvb now,tvbnow,bttvb' @- {- v; _1 o( \- Z0 L
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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/ A) k% v) \. e# f* o/ vThe smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising ) U2 w+ G6 L2 h6 p' ~& J% n9 P& r
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
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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:5.39.217.76+ |! x# Y( C2 b0 E
% a8 N% f; ?6 s, [' H0 ]* F * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.公仔箱論壇' Y1 n: g- u9 |+ e5 i1 O- I% q
* A shockwave from the eruption could have blown a hole in the cloud deck.
4 n4 C: p: P# n) B) V+ aTVBNOW 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。 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.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。, [+ v& U4 U; R* l) y
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
+ n' }$ d5 _+ x4 G& s2 P6 G5.39.217.76It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
3 X9 r. V2 ] t: f3 e: b 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.公仔箱論壇; b. b9 d8 ]7 l3 P5 K% f
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Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
/ Q7 u5 j0 P: d 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。 the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one tvb now,tvbnow,bttvb# z; ~ s0 R$ l- ~# z6 q
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
& b9 ], w. J/ K+ {+ m5 Jthis picture are from forest fires ignited by lava.$ t: c% E( ?- t0 n( A) j7 P
$ I0 V. q+ [" ~2 c# O7 HEtna 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
a* b4 f: b3 _3 n: |( S! T! J+ utvb now,tvbnow,bttvbalso be the oldest-known active volcano.公仔箱論壇+ I( j) y' k4 i* }
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* a: _/ z' f( N; O) `A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
# E% n/ J$ j- O, g! b/ Vand claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.) I/ s5 n/ M! b
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
& B: M: [0 r& F; I8 P& H: L' A" s! I" IThe 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
( D: h m s( E4 j7 Z% B公仔箱論壇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 tvb now,tvbnow,bttvb! N, V: \& I7 B8 S' F( f
of frequent activity. The plume reached heights of around 30,000 feet.
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, r# ?' f! c6 S. Otvb now,tvbnow,bttvb
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s& U. ]8 b7 `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。This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 5.39.217.765 z- A! o! Y0 ~# g) p% b# e2 h
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic 5.39.217.762 Y* J7 w) H* q: s! Q9 w+ e' |
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
( D" w4 F5 v5 T% f: I& fis 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。9 h: x7 V+ h3 V& n2 J6 a% f! ~
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
1 t0 t* a2 q0 ^8 x+ g& w) T) |5.39.217.76stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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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.
+ p( P8 u6 M$ X* r0 @公仔箱論壇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 + v {4 E2 M- V' f
that 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, 公仔箱論壇4 M! K$ q, n1 }" @
causing avalanches of debris into the crater. |