One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 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。# D a4 E3 [+ |1 m! |+ e
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are os.tvboxnow.com7 {5 ], P$ v5 T. D! B1 ?4 h0 D
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
3 Z+ s* |! I( I2 cSome volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
* V1 S, X$ n/ O" d. I$ Q公仔箱論壇erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
" {' U$ S7 }5 f" l& nand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. # O3 I8 D$ k, |5 K* |- L
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.$ f7 j" f) h3 }1 B
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
, b7 W$ T: h- I$ C8 `tvb now,tvbnow,bttvbof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
6 K( ~ E1 l. ]/ L* E9 L- Los.tvboxnow.comtaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash 公仔箱論壇& x1 U$ r' ~: w. x- @
plume reached as high as 50,000 feet.
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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 `: C, t4 g# D5 N+ s* |- H& D* B
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 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 u* {# P. F, j+ Y( Y
years. The island’s jagged edges were created by massive avalanches.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。- }# O f5 T* N8 f- ^3 ?
! z+ l% y3 J6 e( e公仔箱論壇Augustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
) F4 M8 _3 m5 Lof Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet tvb now,tvbnow,bttvb+ z3 l3 \. T, D
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
' o# J) B( H$ ~( Btvb now,tvbnow,bttvbthe 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 # ?% t s Q) S L
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' k+ C) ]; o+ i7 G$ `, w
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 公仔箱論壇7 \5 p0 `. P: q6 S/ y
as a pyroclastic flow.os.tvboxnow.com# G$ S: ~' X& q; O) v# c9 Z
7 k6 {# |% l" |( K/ ZThis 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.
8 e0 Z& l0 [" D: b8 Gtvb now,tvbnow,bttvb * A shockwave from the eruption could have blown a hole in the cloud deck.公仔箱論壇1 B, \( H( h- e1 ~6 C: ^
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.% X G* ^" N( g* \' M
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" }/ M( r6 T0 U7 u9 ktvb now,tvbnow,bttvbAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
0 E0 M k' P2 F: O w5 D) {It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
& V8 z* b% P3 R, o* Y7 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。 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.1 l ~, w# [# m1 `
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Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in公仔箱論壇) c" _7 E, `# E8 m
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
" w* ] z7 \" T6 Sos.tvboxnow.comcaptured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
* k4 ^, C, \# o" c: Y- ]3 Mos.tvboxnow.comthis 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。+ M r" ^# z8 ^6 f' I, a
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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
+ i; B6 @* `3 q$ V: R+ e. x9 dalso be the oldest-known active volcano.
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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 $ e$ X: i9 h$ |' C1 s
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. os.tvboxnow.com) S/ m) e7 X8 ~2 [' k* s, \
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
$ q1 P, W- V+ ~1 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。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 f* L" L" e) k) }; U- g7 F8 A0 ~公仔箱論壇of frequent activity. The plume reached heights of around 30,000 feet.7 \2 c. h2 G3 ^) m6 G: `) Z- M, D; q& ?
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公仔箱論壇, F* x1 [* K o9 e2 _, F: a
* i1 r! z" J/ U+ |. c! c, q& Q: f9 W7 D7 P3 z3 u" V4 B7 `
% |) T/ m0 ]8 i- \2 ^3 `. } 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。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; B* t) P: X2 l( b3 D' ]$ t
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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X) g, }- o4 F* K/ V4 \* E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 公仔箱論壇+ M$ f1 D2 P+ q' }
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
) T$ L5 p6 T9 P6 g4 d9 K; Q# gis 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
. o% O+ s. x8 b( K2 R k. V- Y% atvb now,tvbnow,bttvbformed 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 公仔箱論壇) U: U$ F9 Z/ I8 ` x* F
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.) V% m1 ~ f9 @
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4 G% i8 o& A F0 L2 _0 v! Z公仔箱論壇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. . a5 A; w% E& ?" {% ?
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 公仔箱論壇& P, l8 e+ s, m. y- h% p$ p7 E* q
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,
% s: x7 Q3 a1 t* ^& b- Ios.tvboxnow.comcausing avalanches of debris into the crater. |