One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
! F, N* \: ^7 g L8 s8 f% @& o! s; u% w5.39.217.76eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 5.39.217.760 W% P# }0 P# i# @7 [9 T! L$ n
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.0 ]4 L6 W G- m5 d1 X
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
7 @6 ]7 B( D1 t( l! Eerupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
8 Z" T3 O( y8 b0 M) _! G) qand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 公仔箱論壇0 i/ Q# l& B' d0 w. h9 r
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.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' S& }. G' |) x8 Q9 Q
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
5 N5 }1 p+ a$ |+ n# [8 I" P5.39.217.76of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
) ]- l- h' V! Otaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash tvb now,tvbnow,bttvb% s1 v4 i, @6 {. M; k! |- \
plume reached as high as 50,000 feet.
9 X( w6 k, w8 x2 \公仔箱論壇
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' G9 h; D/ T" V& L7 a Wtvb now,tvbnow,bttvbAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
) ^! `: J6 D2 `( i' ^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。satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 ' C7 X+ a$ [) j3 ]; F% X
years. The island’s jagged edges were created by massive avalanches.
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7 B. W' D2 _7 w- k, E0 E7 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。Augustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring 8 p2 s1 g& M5 }: g
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet + ?$ _( H) u0 ?; ]! [
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
$ `+ Z& j6 t ^3 |! R _tvb 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
0 \4 g3 D2 o' p! n0 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。in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.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。 L% r' S' T6 z! X
9 e& Q) U" C) d7 n* eTVBNOW 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
" n7 \7 F- U8 w! r4 [- Q5.39.217.76and 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2 A- `" P7 g5 A
as a pyroclastic flow.公仔箱論壇2 H8 i% s" U# l0 q1 [
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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:9 {/ i4 Y/ [! m/ V
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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.' n- Y& r/ Z% z
* A shockwave from the eruption could have blown a hole in the cloud deck.公仔箱論壇0 i2 _- u2 d0 n6 i% m( o
* 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. tvb now,tvbnow,bttvb* M/ c* [ e$ \
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when h8 d; v& f, X# w% V
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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% D6 l2 R) Q6 a4 y+ K+ Z* w( DTVBNOW 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。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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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3 h. |! R& x9 S- \8 Y
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 9 h6 W. P6 |$ T) M
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
: G8 |8 y6 v% p. y) O8 A$ ?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。this 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 may5.39.217.76( n- }; c5 J! C: e
also 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 + B# c& Q5 M3 Z% L2 r a: K7 H# }4 E
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.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。 A3 b o* @' e2 f/ ~
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c$ }- j. m9 h2 s$ P2 q) M4 i5.39.217.76Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 公仔箱論壇9 e- k' C6 f2 y( z
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
8 s- K+ ^' p! K2 q: T" r9 P) 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。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 6 \" M1 B1 q7 d! `+ f9 H" A$ e
of frequent activity. The plume reached heights of around 30,000 feet.
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7 C _5 B% p+ H; J% P; M6 _# gTVBNOW 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。 tvb now,tvbnow,bttvb6 k0 j; F {0 h) m2 I) A5 G1 R
+ ~% W4 r$ R3 \2 w/ x 公仔箱論壇- @8 H' h3 Z$ I! z1 Q. a
0 ] F& S% k: i* s* hTVBNOW 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
! }* `7 v, k, A+ G5.39.217.76west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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! W& z: d ?+ y8 g# P' r3 ]3 I1 H) I5.39.217.76Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic tvb now,tvbnow,bttvb+ d1 U/ a0 b6 `
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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S9 d |9 q( M/ gtvb now,tvbnow,bttvbThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
, P+ M, i" s2 h% E( p* c' o( Btvb now,tvbnow,bttvbis 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
$ g. Z% h7 g ~8 Q3 v: s, A, ~5.39.217.76formed 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
# I5 n) X& d2 K: G, xstationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.公仔箱論壇 e* K$ T& d( V
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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.
0 V3 d4 R! w; _9 gtvb now,tvbnow,bttvbA 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
+ s* d: V* ?- |3 Ethat 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, 5.39.217.76; Q- _; |$ ]7 F
causing avalanches of debris into the crater. |