One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 公仔箱論壇, U3 y& ?& L7 U4 b
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
% @9 J, b/ g- `# ^active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
2 _! w4 U; j2 B3 S1 {2 r5.39.217.76Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 5.39.217.76: k+ x- a$ ? @3 d k7 j, l1 a
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
7 z3 `: @# A. K Y! ~' ~4 `tvb now,tvbnow,bttvband explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
/ Z& F& v5 j* H8 h6 i( JThey tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.5.39.217.76+ C" |1 a: G3 |2 R3 ^
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
3 H% e$ h: f% _8 h, p6 e' z3 qtvb now,tvbnow,bttvbof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas公仔箱論壇" { L. z9 p! L" b% `
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
: T2 T+ [8 u, f+ `' dtvb now,tvbnow,bttvbplume reached as high as 50,000 feet.公仔箱論壇9 D# N: P; @$ f! A
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 6 J ]8 t) M! H
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
3 W( I1 W, J7 l; F; T$ z. J/ atvb now,tvbnow,bttvbyears. The island’s jagged edges were created by massive avalanches.公仔箱論壇! M* j4 A# L! i+ x+ L6 |, F
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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 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 e+ n' z2 R5 M# j( D' a
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
2 q: d/ u% v# x! P6 Z公仔箱論壇ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
6 p/ i- p9 `7 c3 k5 l: z$ Htvb now,tvbnow,bttvbthe continental crust, creating magma that drives the volcanic eruptionstvb now,tvbnow,bttvb, S7 ]) q' _+ ]- l) {
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 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。, C, h( w+ s1 }) ~2 \8 {6 w' e
: u) ^' F4 W, p% z, \8 _# 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。Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
: Z) q6 O; f( h& H1 [1 L7 j5.39.217.76in 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。 f Y; e2 H: `- W' D( n
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, x% Z: e, M5 d$ @/ A: p4 }
as a pyroclastic flow.公仔箱論壇% K5 \: S$ }: H0 q9 \( l& |) g/ [
8 C, l: D8 E# G* b( o: h i公仔箱論壇This photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:- w& t7 @3 P( P- z0 B
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* It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.tvb now,tvbnow,bttvb( L$ j( u- W- ?/ Q6 S
* A shockwave from the eruption could have blown a hole in the cloud deck.) k1 Z% m' B: _+ F
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.tvb now,tvbnow,bttvb5 O: H& Q0 W$ U0 c, r+ u
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4 l, R" ]; S1 L+ C3 K5.39.217.76Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
; s+ B+ T# ]; f3 X4 |; ?TVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
9 w/ x: l8 \. j- z* [0 E% k公仔箱論壇 the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.TVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。- R% n; Z5 s7 r1 P" l, V7 ~
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Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.5.39.217.76" P$ l8 Z9 B8 E7 a( O4 o; j& e
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9 U( H0 \) c+ V+ r! r1 A! x/ ttvb now,tvbnow,bttvbMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes intvb now,tvbnow,bttvb8 D% W I" y. S2 `' @ |
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one + a4 z* n1 p; }1 ?5 _, y
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
8 }9 l2 A: a Q: ^3 i% gtvb now,tvbnow,bttvbthis 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 may
" B$ X% `6 R7 L公仔箱論壇also be the oldest-known active volcano.9 _1 @8 x" Z" m
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. e2 m" N7 n0 L" vA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
3 t, e. ^, V. X B. m+ Z9 g; E5.39.217.76and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.4 f0 O/ L8 h; R, x8 |- b |# y' @
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S( w' ~7 U& k公仔箱論壇Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
6 H& K- d. m6 C. X4 J& X公仔箱論壇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 tvb now,tvbnow,bttvb9 H1 J, l& _* {2 Q& a- T
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 5.39.217.76+ l6 {+ N8 P' B- v
of frequent activity. The plume reached heights of around 30,000 feet.tvb now,tvbnow,bttvb' Z' b& q/ D7 G2 \5 c
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 5.39.217.76. d3 t$ L9 Q& C! a" w
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.7 [- e9 f% w! N* K# b
4 x' H7 J- x) K公仔箱論壇Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic 5.39.217.76% N5 l, F9 |# _' M. u2 u4 v
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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! F7 r: P7 N4 G1 ~) W3 M6 }This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
2 M2 A t, i5 w( n% nis 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
! |% E" m. O: X; S( l: D! Z1 ^公仔箱論壇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 : x6 L' r% n8 [4 [
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.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。! e- N3 M0 E! t7 T$ P( J U0 a
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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.
0 B- V# j! q# n$ ^. C" gA 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 5.39.217.769 I9 Z! }! O8 t
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,
3 P+ b. f( q l! utvb now,tvbnow,bttvbcausing avalanches of debris into the crater. |
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