One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 5.39.217.77:8898: F$ b; z3 E1 H' N0 Q1 J
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 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。) `$ J( {) T4 ]
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.公仔箱論壇9 O8 p* u* {& z1 X' }- {
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
) y' E, _+ d# d. x/ Ttvb now,tvbnow,bttvberupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous ; ]- w% c9 m5 x* {7 u& m0 p; W
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
; X9 _+ Z' O3 w: J' h6 S3 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。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
- Z& ^9 Z1 g. d" qof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas5.39.217.77:8898" h: {) ?8 C8 v
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
5 |+ q1 Y8 g0 J1 L0 n; B+ x4 g# d4 Atvb now,tvbnow,bttvbplume reached as high as 50,000 feet.0 y6 H0 r+ T; W" k0 h
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
o( {5 c* m+ p f+ d( o. l6 Ysatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
- ^6 m4 D- G3 _" J$ G( `7 r+ t公仔箱論壇years. The island’s jagged edges were created by massive avalanches.公仔箱論壇# X6 L- _* ]3 h+ J
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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 tvb now,tvbnow,bttvb+ y# p4 c& S8 Y& S0 d" D6 F
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet . p9 w2 L. H2 d2 i
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
8 V2 W2 _) ^) m& ^tvb now,tvbnow,bttvbthe continental crust, creating magma that drives the volcanic eruptions
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: A* h- Z4 ? m2 u P8 u! I! N' nAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano 4 Y' z6 q2 H# j s/ m( A
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.: E$ J/ t9 |* j; ^# z8 B
( K' b6 y' c9 [) J& p8 zTVBNOW 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 smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
: \# ^) u/ z( j% u7 J公仔箱論壇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 tvb now,tvbnow,bttvb! j& |; s4 \7 v4 [. Q7 L
as a pyroclastic flow.5.39.217.77:8898% j. u7 V3 R. z
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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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+ R5 Z+ P3 ^+ T5 h; _tvb now,tvbnow,bttvb * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
6 M$ h" b+ M# u5 d; J. |* y3 X& xTVBNOW 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.
B# B1 p, j5 G- G0 t8 N! h * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
U" ~3 g6 A* g; L( [% b6 C2 BIt 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8 j2 t- ]9 _* R- J, l& I
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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# x+ y: P B! o" b9 ]. \5.39.217.77:8898Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
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captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
7 I1 ]1 ~$ E1 |. s/ h; lthis picture are from forest fires ignited by lava.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。8 ^9 Q' Q5 m' s' \* Z
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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( `/ m& |" ]5 U+ s; f: G
also be the oldest-known active volcano.公仔箱論壇7 z7 V4 n0 O X5 K" Z& o
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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
9 i- O& u u3 @+ W公仔箱論壇and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.5.39.217.77:88982 J) D) e6 P4 z7 q
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" K$ ?. c% R( @. k% n# m* ?6 pTVBNOW 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。Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 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 s+ ? R6 W6 B) [$ k
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
6 N8 ?* G% r" j, b" gmultiple 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 \5 M" M2 x9 e7 n2 Hof frequent activity. The plume reached heights of around 30,000 feet.
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4 ?* m4 Q A1 ~This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 5.39.217.77:8898# v- Y% T3 S6 E8 [* d2 Z2 C
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.5.39.217.77:8898: P) @- R9 z. V0 U2 _# @3 z7 m
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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 ; y0 I+ s: k% U4 S1 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.tvb now,tvbnow,bttvb" }+ }5 O. w! `& u4 B* l' k# L
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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
8 c4 `. |+ ?: ]! ~( Z公仔箱論壇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 i. n6 O: S7 v" G4 b1 RTVBNOW 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。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
% _; r) @# p; q! E2 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。stationary 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. tvb now,tvbnow,bttvb: x2 V" M5 P7 S# d# t$ C
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 5.39.217.77:88982 I; l% r7 m( 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, 5.39.217.77:8898! |' k8 n _* V* @, g# z9 f/ E; g4 _
causing avalanches of debris into the crater. |