One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
& Z7 T* H: x6 J* W4 M2 Atvb now,tvbnow,bttvberuptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
6 q8 m% N1 o+ L% Y1 ?, O+ ytvb now,tvbnow,bttvbactive each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
3 Q$ _2 u4 ]' s x7 P D) ?Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
! J" L; E+ c( ^2 `tvb now,tvbnow,bttvberupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous tvb now,tvbnow,bttvb4 ~, a3 L' b& b5 D8 Z" N- ~
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
9 Q- g* V$ B& Q/ l# L( w3 a0 q$ Z8 t6 `; itvb now,tvbnow,bttvbThey 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 公仔箱論壇4 l# u% v9 c; D& ^* R
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。8 Z; p9 I$ ?+ J$ E
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
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a ~3 l3 K; n9 J& ~' xtvb now,tvbnow,bttvbAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra ( q/ H2 k8 \9 N# e. I" u
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 tvb now,tvbnow,bttvb n7 x8 k0 f. q4 L) {
years. The island’s jagged edges were created by massive avalanches.
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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 公仔箱論壇" Z: x) D; }+ K' ]5 y1 t
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet - Z) E( [2 Q0 W( I& }+ l+ b3 i
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of 8 r. [% ^+ I0 @: N- Q" j# i
the continental crust, creating magma that drives the volcanic eruptionsTVBNOW 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。7 U" H; f8 E9 o! ?2 u
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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。& e9 t a" Z' l; t9 K
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.5.39.217.769 k9 W$ X$ B5 I5 L4 C$ V
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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
& [0 s: d# K7 j- ?+ t2 T$ Y' ]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。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 {* [6 _6 }# e& oas a pyroclastic flow.
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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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. G. O1 H( J! V5 s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.
8 A, s W( ^. e8 Etvb now,tvbnow,bttvb * A shockwave from the eruption could have blown a hole in the cloud deck.tvb now,tvbnow,bttvb2 q, Z; g" i! _6 t7 P! v
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.5.39.217.76( l4 R- X( y$ Y: Z( F1 Q
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8 o2 ?! r0 h, V6 z- S' \tvb now,tvbnow,bttvbAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. % \- |. X- }. H" c- ?* s
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when公仔箱論壇4 ]. j4 r2 O% e" a
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. T: s1 I3 ^' U$ c$ j
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$ w& v9 e: A2 Y! v7 utvb now,tvbnow,bttvbMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in) f( i. |, n$ i8 R8 i
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
, T' r1 U% R4 ~# F1 R! l4 ^; Xtvb now,tvbnow,bttvbcaptured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in tvb now,tvbnow,bttvb3 |! z' T1 g! [- `( d2 l- U( c7 x
this picture are from forest fires ignited by lava.公仔箱論壇; O* J1 Q% U9 F1 @8 H" `
- u' ?1 U, V1 B; W. H5.39.217.76Etna 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 may5.39.217.76! K7 g; I# f, u2 J/ } j5 Y6 R
also be the oldest-known active 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。: r# B! U$ J# ~
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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 5.39.217.76 E1 Z' \- b* i1 I
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes. j- Z; a) Z- P
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* S L: n* T6 O( Mtvb now,tvbnow,bttvbPopoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
- E+ X% E# C+ \3 O5.39.217.76The 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,bttvb! J2 d4 J' K" r, ~4 R
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 公仔箱論壇( v0 J0 ]( S* j4 v: @
of frequent activity. The plume reached heights of around 30,000 feet.3 L" O& Q7 d( |' M1 l
; I) g& Q6 h' R9 V! e ^% NTVBNOW 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。7 n+ X, c0 e2 H4 `# ~6 f/ a- U' L
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 公仔箱論壇: C/ w m! @+ I: ]3 ~% M7 u* Z
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.5.39.217.764 m [- X2 P- a) ^2 ?. ^ t
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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 公仔箱論壇5 [# j5 b5 X; K: A+ C ?
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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% ?- g9 t& M1 {8 [2 A I9 htvb now,tvbnow,bttvbThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
7 u) D. Y- ~; s% ]4 b/ W& s4 O6 s Jis 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
, f% G- ~9 f7 T1 q1 _1 S6 K5.39.217.76formed 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 . l( Q4 C. o1 G, w, ?3 {( H( R; |
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.% U- n' f! b8 g8 k. }1 z" F
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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. 5.39.217.76$ L4 n J9 y5 C1 s, F% Z! O
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+ \$ W' E3 l5 Y! y8 [公仔箱論壇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,
- D; s7 D1 R/ |2 f% K5 B! d5.39.217.76causing avalanches of debris into the crater. |