One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
/ z* X- a p3 s! B公仔箱論壇eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are tvb now,tvbnow,bttvb* `. [ u( n, K' M
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.5.39.217.77% X7 `% P( \3 f" T& t
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
0 G2 ^: Y' g1 M& ]! Terupt 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。; k. e5 c/ [. X0 |' i$ |! `0 H
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
; U+ w% g# c. Z; m* w7 x' sThey tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.% y0 x# f: ?6 e4 Y
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
: u. O. s# {/ R7 V! m: D6 T/ f7 {of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
2 E. z- I$ v, S. h; v& ^; Y" D公仔箱論壇taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
: Y: h1 x, d- K2 t. l公仔箱論壇plume reached as high as 50,000 feet.
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! S7 }/ V" |) i1 ]. n0 U. zAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra tvb now,tvbnow,bttvb5 H& z1 ~( M! V, q! m/ i0 k) B- A
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
: x- j5 b5 S+ f! u, e: b0 l$ g' {tvb now,tvbnow,bttvbyears. The island’s jagged edges were created by massive avalanches.
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9 t- R' v! x. y) AAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring 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 g2 c; H) ]- f
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
2 a; Y8 {. T0 [ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
9 L9 r9 b$ s! U7 [; [5.39.217.77the continental crust, creating magma that drives the volcanic eruptions
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano 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 n1 _2 {! @# ^; ^
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 公仔箱論壇& Z& M$ z2 ~* p: P' _- N. c; [. }
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
9 Y; E* _# `* vtvb now,tvbnow,bttvbas a pyroclastic flow.
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' r% B3 t. n, d& Z6 p公仔箱論壇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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* It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
; m4 O2 K! _& Q* m; qTVBNOW 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 shockwave from the eruption could have blown a hole in the cloud deck.* k7 @- Y' p ]) |6 G6 r/ ~" A
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.tvb now,tvbnow,bttvb& T) E' P4 F' X- `1 c' Q% C
1 L6 j0 |! x. [5 Ltvb now,tvbnow,bttvb tvb now,tvbnow,bttvb; y0 e" a; @; O
0 }- {6 ~" y6 f- o: n; uTVBNOW 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。Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
" f( t4 l# W/ eTVBNOW 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。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! B" ~+ z' d8 {
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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& s% q. }4 I7 R1 u* K% \5.39.217.77Redoubt 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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& ]" H4 s8 z0 x3 ^1 | L" A( yMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
, R7 M% o1 g) {3 c7 I1 e" b% e' {6 ptvb now,tvbnow,bttvb the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
5 }% A0 I" \- C5.39.217.77captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
9 D% W2 [7 h1 }$ C k/ m( a* u0 Rthis picture are from forest fires ignited by lava.
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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 mayTVBNOW 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。* B1 o, G/ c# t8 o
also be the oldest-known active volcano.4 W% f5 x n7 F$ f
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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 公仔箱論壇5 K/ F2 ]: K% F$ h f' g* g
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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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
* Y. X3 g. W4 n- l4 \& ^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。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
! h6 {7 U$ l3 w% } n6 R; cmultiple 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
9 X: X* b% H5 |; V; F }; ktvb now,tvbnow,bttvbof frequent activity. The plume reached heights of around 30,000 feet.
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the tvb now,tvbnow,bttvb; B( {3 z4 Q1 R. z2 S
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
; L- Y( v R3 f0 J$ o; Z公仔箱論壇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 . w! d8 K* c$ G4 z
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 5.39.217.770 L/ ^: N9 \9 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 tvb now,tvbnow,bttvb* k: I; D6 u) D
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.5.39.217.779 m) m1 v, r6 v/ X
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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. 公仔箱論壇. X) j! u+ n* r9 T8 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
. w! o8 V; r0 A9 R$ O2 i9 \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。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, 5.39.217.77) I& }; `- m) G' Z) k) g3 I! \. ~
causing avalanches of debris into the crater. |
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