One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
* Y6 W/ @/ j; r+ }, M' qtvb now,tvbnow,bttvberuptions. 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。+ N7 l% Y/ H8 T# M
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1 H5 ^ E7 T, ~
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 5.39.217.76. k% |/ J6 V. c# V$ ~6 \2 V
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 5.39.217.76$ |( D- t E8 p. B. @& V8 L' ]
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
# X. l5 X; v4 v' v9 g$ c/ q1 xtvb now,tvbnow,bttvbThey 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 5.39.217.76; l7 Y# |" v3 q, k0 T
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
8 k! \/ F C7 btaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash , t% t* d# w0 o: I# M* T
plume reached as high as 50,000 feet.
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& ?$ ]# A5 r# Z, m3 B9 OAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
, m3 a7 O Y8 w; s7 R% f7 bsatellite 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。: k! ?) Y2 r' g2 W; ^* p
years. The island’s jagged edges were created by massive avalanches.5.39.217.76% l Y# s! K( M1 ~+ z. g! s' y
. d5 M$ `" w: m( }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,bttvb2 s! b7 c% V/ @# L5 a
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
0 }) e/ W; G6 w/ g* ^! h- j1 r5.39.217.76ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
$ C- H) R6 o* sthe continental crust, creating magma that drives the volcanic eruptions5.39.217.76( V5 v" w; `8 G$ F1 j/ l* `
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1 j2 F* y# q9 {1 D6 l公仔箱論壇Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
8 [3 i) f. Y2 m. Q& q3 H" |$ a- @公仔箱論壇in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.tvb now,tvbnow,bttvb! K9 u, b3 h( n
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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
) a! Q4 O/ B' C/ }0 M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
0 D# I9 ?8 ]- I: U- v5 q( g6 D% P3 [公仔箱論壇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3 u7 g# p+ V( }8 V. ~# }$ U
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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.
. J* F/ T4 w; W6 g$ t * A shockwave from the eruption could have blown a hole in the cloud deck.tvb now,tvbnow,bttvb; `' |. q8 c; l( c: C; s! V1 Y6 k( Z
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.5.39.217.762 B3 o1 I3 o4 `
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
- z* [7 O+ K, r2 ^$ m6 l/ R, iIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
/ ]9 f5 I: |5 a/ q" I& ~9 a5.39.217.76 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.& ^: `! v" c5 [* ?3 i0 Q
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0 T: x: s; Y. y D% f! p/ oTVBNOW 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。Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in5.39.217.768 |- T) q: D4 k% N/ u$ g/ H
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
% ~. [* Q% n. D, v& [captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in 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。( K! K0 g7 f' |2 t7 ~/ {
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 mayTVBNOW 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。' Y1 l0 ]. B( [+ z. B8 y5 K p
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
- M( k3 v. Z* 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。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.
/ X" g0 ` Q9 k; F9 v6 j+ \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。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 5.39.217.76+ [# \5 K0 `% ^+ ~
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 tvb now,tvbnow,bttvb' b! P3 U: ? C |+ Y
of frequent activity. The plume reached heights of around 30,000 feet.
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/ W5 y6 y% _! G7 u& mThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
" e; F2 ~4 l, F* K$ ]7 jwest 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
# K$ |1 e T$ U) R' Cflows 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.7 a. W! w- Y5 U( [4 ]9 @( @+ i+ l
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2 G+ u6 c' X% Z. u- F$ U, jtvb now,tvbnow,bttvbThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
/ V C/ i: l# P! h% z! s. @5.39.217.76is 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 ( V9 G, E: R0 K
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 / f$ r8 e" Q6 L- W; ]2 k
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.$ P% _. A/ V9 I: j* H0 }
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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.
# [5 x$ d4 y9 w. N9 oA 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) F' y+ }- c& m# z/ y C
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, * H( t1 [* h# u% X
causing avalanches of debris into the crater. |