One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic tvb now,tvbnow,bttvb' Z1 z9 u; r' L* R3 T2 y" F8 a
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 3 V0 K0 {5 b1 \$ t* C5 Z; ~9 h4 E$ l
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; ]: e' c! J* O7 ?& h
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
' ~$ G4 k7 g* T" }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。erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 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。9 j( U) `* }5 h$ P( Z+ y( n' g
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
8 R! {) j% x3 Z! V( Xtvb now,tvbnow,bttvbThey tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.) T, M+ Z5 L$ J$ i
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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% @8 t t- e' y$ A0 b; m4 B: S+ P
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
) S$ Q: v/ _5 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。taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash ! V6 `9 G N: y# g
plume reached as high as 50,000 feet.
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8 K! ~' g4 s/ z( A( U( R5.39.217.77Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 5.39.217.77' e, N k' z+ R, K( o* K+ a
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
3 }2 m; t$ O- E8 H" @/ ]6 Btvb now,tvbnow,bttvbyears. The island’s jagged edges were created by massive avalanches.* u- U+ r; V6 ~( `% |
# j8 T6 {9 G' y Ytvb now,tvbnow,bttvbAugustine 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。* o. k5 j+ B4 |/ j6 n
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet ( a* o& e. x; B0 ]3 C8 v: D
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
5 W4 B- c2 g7 ]* w5.39.217.77the continental crust, creating magma that drives the volcanic eruptions- X3 z: N. i `. a) a
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" ] z/ e2 N+ B }/ HAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano 5.39.217.77+ Y& c( s5 \4 I. L9 {# O" f2 m0 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* \. p& j3 ~* I1 Y
3 Q( i" a/ U. E8 TTVBNOW 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
8 |- E5 z6 y0 H5 c3 h; D) H5.39.217.77and 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3 m' e& j, G* I; b9 {6 D6 h; m4 b
as 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:公仔箱論壇% [* ^ U! A. l+ R" `! h
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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.5.39.217.77$ f9 S8 b, V8 ?/ b- Q9 \ I
* A shockwave from the eruption could have blown a hole in the cloud deck.公仔箱論壇0 a: J7 ]% O8 F0 ]. D$ u+ ^
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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: m3 y/ D2 j* a0 a( g, X* F5.39.217.77Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. tvb now,tvbnow,bttvb( l6 U! m( v: I' E$ T3 ^
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
3 L1 g0 G m& v2 A6 b# }- u4 T the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.公仔箱論壇: }5 \# Y7 \/ {9 a z
' p0 n+ y2 a# ^/ x; O1 DRedoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.0 w% x( j2 m% g
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2 l( L; o5 c0 o3 m* t& ^7 GMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
" t6 k' d% X; q. k8 c! \ the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 5.39.217.77( u+ ]1 Y$ l/ w+ }: u) H7 D: `! L
captured 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,bttvb8 s. B, z4 ~* l( R& ~: `
this picture are from forest fires ignited by lava.
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7 ^+ I$ G' O/ Y5 t* y6 Q: ]* z公仔箱論壇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
2 ]. R2 E3 h2 }" U% N5.39.217.77also be the oldest-known active volcano.
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$ a4 r6 j3 Z1 s. Y q公仔箱論壇A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high tvb now,tvbnow,bttvb& @! Y' R7 Z; w
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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+ ]$ s' { g3 h2 n# 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。Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 7 s, r- x, l6 U
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
3 b+ S) J7 w& V- w8 Q9 F; y公仔箱論壇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 ) h4 U. o: C8 {6 \4 D0 q
of frequent activity. The plume reached heights of around 30,000 feet.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。# i8 ?% m M+ H5 ^ N0 [
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$ N) `, ^9 ^$ y" e: [7 j公仔箱論壇This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
0 P @9 `# I! x9 [+ k$ e/ iwest coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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$ M2 B) Z# r' D( L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 . H! S7 ~0 A3 l# V# g* f: _" {& y
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 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。$ H- m j: A+ Y+ M1 T6 A
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 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。( C8 g8 c/ S. s$ g1 o* B, a E! x
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
/ g( I* K4 ~. C' V& q' E- t公仔箱論壇stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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- j u4 {: e ^0 z O0 [( Jtvb now,tvbnow,bttvbNASA’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.
}9 n7 z8 ~' n5.39.217.77A 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 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。- P/ r% C* m" O2 P+ e3 n# L
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,
) m) O$ b& v+ O5.39.217.77causing avalanches of debris into the crater. |