One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic * C& x. p) D0 v7 X+ n, h
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
/ @2 x+ C. f0 e6 Xactive each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
) z" e2 \' w1 N# {% G公仔箱論壇Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 5.39.217.770 n7 Z+ D, \! w4 x( g8 X; m% p) K
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 5.39.217.778 Z8 R& w n+ E( A8 a. o
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 公仔箱論壇1 u" G8 ^- c: s9 U4 }( w2 t$ v
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above tvb now,tvbnow,bttvb' W. u2 [: n g0 i. c
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas5.39.217.77; X j- G) f# b+ H; H# T
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
& z* A/ Q" @/ Y7 Lplume reached as high as 50,000 feet.
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9 w+ }: T+ v) R) m( ~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。 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。/ w2 T' p1 a2 Y1 `: Q) O* o
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
( q J9 B0 d( G8 p# c% y# h# 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。satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
( H: n g R+ l9 r公仔箱論壇years. The island’s jagged edges were created by massive avalanches./ F" @0 B0 W( J3 x2 W1 R1 M
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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 5.39.217.77/ ~0 z3 u5 K6 k4 I
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
! h6 ]3 Z' q, \, F, W2 n/ a3 }. Gtvb now,tvbnow,bttvbocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of 5.39.217.778 A P" K$ ]0 D: q1 L5 I
the continental crust, creating magma that drives the volcanic eruptions
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4 b8 J$ M! `- A5 `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。
0 I, Q/ i/ B5 y( s. F 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。
/ h, f* p; X& ~6 N6 q) _( 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。Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano 1 X2 |4 S- [& W! u: Q, H* J: Q6 H" {
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.5.39.217.77& i4 a; `3 D# w: i8 K( `- m
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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 - b2 g3 A/ P) E) 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 & C& m6 n) o u' `/ G& D
as a pyroclastic flow.tvb now,tvbnow,bttvb2 W. p U% @: }& h, ]& V5 Q
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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:公仔箱論壇- R) o+ n; T( e8 [
) l8 \1 K& R( X E! @ m7 ~* h公仔箱論壇 * 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; @3 r( i; t2 y A! Q+ x9 y
* A shockwave from the eruption could have blown a hole in the cloud deck.
g! A+ y9 e% d& C+ e8 b5 I5.39.217.77 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.公仔箱論壇! C$ _: O+ A4 E" y! `+ N
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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。# D3 h+ M) V V
Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. 5.39.217.777 W( B( j" Z" _# t$ ?
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
% k9 [: N. m$ t# j* v: g+ 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。 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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( E: B. a( V3 f1 T% G: J, eMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in5.39.217.77# t& \, Y8 o, @1 J
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
2 d, C9 K+ N& S- B* G8 x; Q& Kcaptured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
1 @4 g% Q9 C( d$ L& h% rthis picture are from forest fires ignited by lava.
, W- B; J/ b! P& q- ^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。
2 F' S- v% f4 ]: T* b4 A* |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。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
* D5 n `' z& R4 ~5 dalso be the oldest-known active volcano.
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& I6 x2 r1 N+ n' U0 FA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high 4 _; w; Z7 W# S' i' T0 @
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.公仔箱論壇/ e: v/ F: @+ B2 V" X
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5 X; x5 h; k8 }+ h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.
1 k6 p- S5 L2 @- P" {0 cThe 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 5.39.217.77 Q8 ?1 S; q% [$ P
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 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。2 l" T P8 a! c# i0 z, b
of frequent activity. The plume reached heights of around 30,000 feet.
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! e8 A; C' _1 [7 _- b. [! gtvb now,tvbnow,bttvbTVBNOW 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。( g1 S& b' a7 [7 R F* r
This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 4 y: h. W2 ?# U4 g1 F% ?' |6 _- Z
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
+ o2 f8 P4 p, t3 n# 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。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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- T( u, M! g4 r9 @7 G- E公仔箱論壇This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
( i* @1 K5 I4 f% H- t7 f- hTVBNOW 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。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
9 i) f' ~2 T% B3 a5 Z% l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
( P0 j- O7 e3 Y/ j- B3 W9 a2 p& ptvb now,tvbnow,bttvbstationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.tvb now,tvbnow,bttvb& w' \( z) H' D4 U
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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.
5 f& Q9 r Q9 E' q" E& g8 JA 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 公仔箱論壇. R2 o! C4 K; u
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 q$ G- I/ n/ w( b# B/ R公仔箱論壇causing avalanches of debris into the crater. |
發表於 2009-12-22 08:34 AM
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