One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 2 c& s: |1 l& v/ Q/ R Y8 D+ b
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
: M* n; f5 _/ p, Z7 @os.tvboxnow.comactive each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
' Y$ d4 c, l- {' s3 }- A公仔箱論壇Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 公仔箱論壇2 r5 U' H! q8 T( O! N
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 公仔箱論壇; m+ x' F5 B& I& X. o- E( m6 l# }
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 公仔箱論壇! G' k4 \: s' l& \2 Z
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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) h# J z, M& ^; XMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 8 A( B" B% G+ A' }; k0 _
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas' X. i. R8 I% A5 k5 G& b5 n) n( R
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
& {) s/ A) |0 F& k! Y( B7 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。plume reached as high as 50,000 feet." g- R+ _+ C/ t! K0 w+ n m: K1 r+ G
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
3 v8 U0 r4 M, q: ]os.tvboxnow.comsatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 tvb now,tvbnow,bttvb) N* ]$ B/ o% ]5 ~4 X* l2 U7 n X
years. The island’s jagged edges were created by massive avalanches.公仔箱論壇3 N3 S2 ]" B+ W" S
0 \: B+ W. [' m. Ros.tvboxnow.comAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring / F7 z1 Q8 o2 |1 H: q) d+ i% z
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
5 B/ i& d7 [6 O% |os.tvboxnow.comocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
- E9 o7 G# A0 ^4 d: ^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 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 os.tvboxnow.com0 }/ |! X2 v' {. ^# B- {5 D2 a% }
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.8 E% z7 W [' M" h* x% d
5 u8 K2 J r, K. @2 iThe smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising 7 v! x* [7 O$ y |6 o$ U Q
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 tvb now,tvbnow,bttvb& @4 o( N8 n* K" A3 _& j) ?* S
as a pyroclastic flow.tvb now,tvbnow,bttvb& m9 _$ o1 q; d# g- U; ^
- [& z6 O9 H0 f" L6 C0 p; wThis 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,bttvb5 \# J5 x G- o9 `- o
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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.4 J8 l* {4 |) J) F
* A shockwave from the eruption could have blown a hole in the cloud deck.公仔箱論壇) J n( I, b' U- w; M1 Q) B
* 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.
. E, t1 H' Q) t; Q6 y* v1 C/ Oos.tvboxnow.comIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
2 K$ H f0 f( V0 w公仔箱論壇 the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.2 r! s/ I7 e. l2 |
; ~7 o- g, M+ z* j' xRedoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.公仔箱論壇0 o$ e7 z0 l! v/ p) L
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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+ G2 h) t5 X: e1 _9 ]" F/ l
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
3 _# C# j) o4 A" P, I+ H8 P3 U8 b4 ~captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in i. @) | f( ^7 |7 x; J
this picture are from forest fires ignited by lava.tvb now,tvbnow,bttvb' p- y& C1 {3 Y6 B6 k
+ _ d7 {+ }' F0 a" q" A4 ~! }# etvb now,tvbnow,bttvbEtna 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
9 [5 o( I3 Y2 M7 F9 W7 y3 @' ^公仔箱論壇also be the oldest-known active 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。0 u( Q) x3 d8 k9 R
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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
' B9 g2 o2 I- e, k, @; `8 Yos.tvboxnow.comand 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.
( V. V0 u7 v4 o1 a2 N4 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。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 公仔箱論壇% Y6 i; A/ G0 {/ ?
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 % u. _' X5 B2 X6 T
of frequent activity. The plume reached heights of around 30,000 feet.tvb now,tvbnow,bttvb) S$ {; w1 j( a0 m8 M
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the os.tvboxnow.com# T: w* {( P1 o$ [
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.公仔箱論壇2 G6 x$ D: @2 A1 V1 K8 j5 `
" W8 G' |! V4 w; u; I2 ~3 K5 X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 tvb now,tvbnow,bttvb9 `( \- O, d" J" E& Z
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.8 u' ^7 Y) Y) \) f& a
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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。% p6 [" @! t) e3 J# y4 w1 J
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 8 I5 f* J9 q' a6 D# `
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 os.tvboxnow.com: z+ L% f9 x) [2 ?( |% r
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.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。1 \- J3 [- X/ t8 p# k& j
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) f- `1 k! {2 A7 Y' `: rNASA’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.
2 B) O5 F" N7 T8 \ yos.tvboxnow.comA 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
" Z9 ~" X. e5 y. L9 ~7 }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, $ t, f1 ]( |& [3 a
causing avalanches of debris into the crater. |