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。6 B! K% {! n6 L! @9 Q# I6 @8 H
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 1 F$ l4 y5 M. D* z# G
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
' P s/ D7 x1 `; H8 h' |6 Jtvb now,tvbnow,bttvbSome volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
# F. D$ B" ]8 a6 k6 @, f' j8 jtvb now,tvbnow,bttvberupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
9 K( m- V+ U. b5 j! Stvb now,tvbnow,bttvband explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
3 ]4 w8 x/ i" E" p: V6 Owww3.tvboxnow.comThey tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.% i# _ ]; U4 J
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
! \5 z% C9 P I; uTVBNOW 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。of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas+ _( c9 B2 d) K9 U
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
7 @/ X |3 [2 m* A8 V3 dtvb now,tvbnow,bttvbplume reached as high as 50,000 feet.
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7 j0 R" _0 _. t2 c# Xtvb now,tvbnow,bttvbAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra tvb now,tvbnow,bttvb# W, C$ T- a# X% k: E8 e
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 / g9 o( l$ g: x M, \# j- O' F
years. The island’s jagged edges were created by massive avalanches.
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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 tvb now,tvbnow,bttvb: C( J! T: X9 i# D: Y8 B% \6 m8 h
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet www3.tvboxnow.com0 y/ [+ H2 H. H! v! ?* C) N
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of www3.tvboxnow.com, ~- {( I7 m+ ?7 V, K
the continental crust, creating magma that drives the volcanic eruptions
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1 }" U; x* Q8 h" w }Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano tvb now,tvbnow,bttvb* e; J `! ]& P1 q! p
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。0 _' i: n; v3 G3 J7 M
) P) W) i3 T% @' v' n$ X: V" w公仔箱論壇The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
: F" t% n- R2 \www3.tvboxnow.comand 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 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 D. k/ s. b+ }- {0 m
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:& r- F3 _" m% A- q! s0 }* Z+ C
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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.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。4 F3 u" ?4 z: R
* A shockwave from the eruption could have blown a hole in the cloud deck.
1 v; V2 w* w. k U4 Vwww3.tvboxnow.com * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.公仔箱論壇1 S" h1 V E* b# J7 _) e
tvb now,tvbnow,bttvb, V- \; `8 F# |% F& q& \
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' Q7 l, F1 X) CTVBNOW 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。Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
- A2 B. q+ l% c: _/ g( P6 Z# j6 iwww3.tvboxnow.comIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 whentvb now,tvbnow,bttvb: N, S' f1 Q$ k% |2 c3 x$ L9 j
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.
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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 inTVBNOW 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 ^+ X1 {5 M/ }
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one tvb now,tvbnow,bttvb9 c3 s) b# I# Q
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,bttvb4 h( `! E; s3 Z' `5 R/ D, [( z
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 may
( X2 u8 M/ M5 p& L+ ~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。also be the oldest-known active volcano.公仔箱論壇& n" k+ `0 j- B; k4 v
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. B8 g3 S% a# T1 Rwww3.tvboxnow.comA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high - h4 a% W! R9 C; ?9 q. \
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.
# N1 G2 g# i6 Y" qThe 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 www3.tvboxnow.com+ d2 S& \5 v' V1 E7 F
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
3 n5 f! v _! R. n7 j C% S# mtvb now,tvbnow,bttvbof frequent activity. The plume reached heights of around 30,000 feet.
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6 w1 o& q# K& ^0 w5 y% q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 # i% E; X) [- e9 E; m) R; d
west 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 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 C3 |3 O+ j! g0 ?6 Q- h
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
! r. [7 q, V. C7 {; L& Q# PTVBNOW 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。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 公仔箱論壇2 f& ~# M0 {0 u% a( I' n% h: b
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
( c) u& W( I7 G0 p# w& S( C" I5 ~公仔箱論壇stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.tvb now,tvbnow,bttvb/ j9 p; W4 {! B# A) v# L
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N, T7 J& {9 [* {8 \www3.tvboxnow.comNASA’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. & A! j7 e) a0 I0 p9 w: I% a
A 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 2 ]- t% R% G7 i; J2 T& M2 v9 }
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,
' |9 T% S0 ` ~" L! x' 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。causing avalanches of debris into the crater. |