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。5 u: K! ]* x/ K ^* i/ h% c
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are ) G7 e j, v6 H
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
. E7 H7 @! m3 L( i6 C1 ^$ Y5.39.217.77:8898Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 公仔箱論壇1 h. s! S0 N& b M( C. p" I
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
3 \% o6 I* w2 L0 BTVBNOW 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 explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
% ?: v0 J& y$ E. O% K公仔箱論壇They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.( a: G9 O$ j1 X0 s; V. U4 S/ M$ v
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+ p1 u: S! A6 Q$ Stvb now,tvbnow,bttvbMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
' N# g: C( S+ Jof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas# f( c3 N3 B, n# [4 m; g1 K1 e2 E
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash 5.39.217.77:88980 J5 i; ^1 L( W9 H1 V( M z
plume reached as high as 50,000 feet.# F$ e+ X: e7 e8 j1 Y8 x+ Z
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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 |+ v0 c! B3 l# m- ssatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
q& p# H9 C% ]0 a: Tyears. The island’s jagged edges were created by massive avalanches.5.39.217.77:88980 T7 }1 @$ X4 W" E- _ I5 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 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。( ?; Y2 @( R! w' K6 ?" V
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet 6 A: ~- O) F+ ~2 P' P$ N2 x
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of " p b' v/ S+ B' q* O4 ]' u
the 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 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。" W1 `0 d3 u2 A V
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.tvb now,tvbnow,bttvb8 W% z1 c' h* Y, {5 A* o. S0 w5 n/ w1 P
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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6 i4 @/ O8 e# v# p( D
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
3 c! L5 Q) c& S+ u1 ptvb now,tvbnow,bttvbas a pyroclastic flow.公仔箱論壇 P' P5 V1 v! p+ |; u* Q
$ i9 y7 }3 X/ N% ztvb now,tvbnow,bttvbThis photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:tvb now,tvbnow,bttvb0 d0 [1 [( T% y! Q
3 t ?) d: r3 f+ k E/ S; C5 `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。 * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
0 e8 O$ I: |" n公仔箱論壇 * A shockwave from the eruption could have blown a hole in the cloud deck.
" A) G4 ]) X4 S- ITVBNOW 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。 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.) B" U4 C! v% F7 `
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. 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。" ~$ V: g3 c. T
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
0 U+ J! i0 k3 h: K7 N# q: k3 }tvb now,tvbnow,bttvb 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% U6 }" v" L- l
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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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2 F" O; i# V' E5 N/ s2 M8 M- E公仔箱論壇Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
& @( w/ a* G g# n- m公仔箱論壇 the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 7 g4 M6 g5 m/ B) J5 J; Z
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
6 q; N0 F5 z0 gthis picture are from forest fires ignited by lava.
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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
2 {7 k6 @( q2 C! Q, ?" \4 ctvb now,tvbnow,bttvbalso be the oldest-known active volcano.tvb now,tvbnow,bttvb$ M- B/ P7 O5 f6 n) e
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8 t4 \) s+ R6 e. x @A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
. s7 _, r' i2 j7 s# g8 O' y. sand 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. / K+ s7 \! C* g( x, r
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 |5 G9 f+ g, P4 ~; 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 8 X6 G9 K& b/ p% P! S8 Y g8 a
of frequent activity. The plume reached heights of around 30,000 feet.
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/ g! C7 @8 g) Y, utvb now,tvbnow,bttvbThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
6 S' \. k7 a" K1 H: { `5.39.217.77:8898west 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
$ M5 ~8 A" i5 \3 j) i$ k+ o \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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3 N: }/ C7 r/ k! ?# 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 公仔箱論壇1 X2 M5 u8 `- k
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
' W7 S" X t9 }, L' d/ T& d4 Ltvb 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* T0 M. r3 {8 C% R
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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1 K* }; ]: F0 [' ?: D- O; VNASA’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.
. K' x; C. m: H5.39.217.77:8898A 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1 K' y5 @1 I- k
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,
2 X8 i/ E: a6 @# R( k8 \: |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。causing avalanches of debris into the crater. |