One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
9 V9 M2 k) X7 f3 Peruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
% h t: h4 f) L3 m9 o4 mtvb now,tvbnow,bttvbactive each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.公仔箱論壇' W }9 u, b9 W- |9 O& q+ p( v. O8 L
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
1 t! U4 j+ U* P, E2 f7 _erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous ) S; v! I, B% h$ x
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. tvb now,tvbnow,bttvb7 L4 x/ r! z7 J
They 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
# [) c+ ^' A- l. U7 F( R公仔箱論壇of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas: I* J. T1 D- p; y
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
' |- w0 }6 Z0 ]/ _5 ~4 @8 G9 W/ ^plume reached as high as 50,000 feet.5.39.217.77:8898. ^, W/ [: k' x
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0 ], ]8 W$ e1 D/ CAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 5.39.217.77:8898; [- |9 g V+ B! W9 T4 p; m
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
; d9 X2 c3 c2 f& S- 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。years. The island’s jagged edges were created by massive avalanches.5.39.217.77:8898$ Z& q' R3 a+ S' d" s
& s/ @4 W' a1 ?0 w5.39.217.77:8898Augustine 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。& c; s1 R+ S* M! j
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
( ?4 G" K8 G* J" I公仔箱論壇ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
: r3 J( g: ^" J+ P公仔箱論壇the continental crust, creating magma that drives the volcanic eruptions
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: @& x+ \# q1 C) c% i5.39.217.77:8898Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
* H& T& i2 g6 JTVBNOW 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。0 K( W; j: j; r( Y% |9 [
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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 tvb now,tvbnow,bttvb( d$ [2 a8 O/ `% A: H' x8 C1 I
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 5.39.217.77:8898; X4 W8 z. J* X- K4 k
as a pyroclastic flow.
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* W7 G3 t0 N6 l, m公仔箱論壇This photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:
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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 X- l3 c6 H$ H2 E0 n" y
* A shockwave from the eruption could have blown a hole in the cloud deck.
- g8 U& i" g* T: e* c) r+ ]) D * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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2 M$ W' ~7 Q. F, J7 J1 o; n2 C公仔箱論壇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。5 g$ i7 G1 ?# w/ k7 \
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
4 d8 ~8 O6 D& o1 t' C, e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.+ {$ r( W( E7 l# `" R
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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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( H' N' B r4 |. x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& Y0 k r2 G# R/ f6 p' y G! M+ W3 |
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
/ E/ b! W- m9 s4 l: T5.39.217.77:8898captured 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,bttvb8 U& F: h0 z @* C* @. M0 v
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。' Q8 F( `4 t, t1 @ S
also be the oldest-known active volcano.公仔箱論壇# R. p% y9 g; ^; [: o
8 Z4 g7 d9 C3 f8 Y& U. t) f& ?2 e 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。" B: E( ~- O, W' Z6 C
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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 9 i4 B1 J( j% G6 m
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.% j! {4 d# A2 l+ R( P! b1 z
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 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。+ M7 S) ?" A* y! g5 h( F
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
, @/ ^% f: c$ R8 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。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 公仔箱論壇2 d2 I+ ~" {, I& i# b3 r3 K! f
of frequent activity. The plume reached heights of around 30,000 feet./ a5 C# R) _* [: @' L2 _
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7 ^3 l$ d& F3 }& OThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the " A! O" z$ Z, x. z
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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+ F5 r O5 Q' [9 f* v) KChaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
, _. A d, W8 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。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
3 E0 K* |2 Z1 W$ r+ O5.39.217.77:8898is 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 5.39.217.77:88980 _1 F+ S8 W6 G4 T4 W1 ^8 ?
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
" O; P7 Y0 O3 _4 }2 ^7 ?, ^7 K. g公仔箱論壇stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.( C5 e. A7 O! j1 @7 F
. Z5 M# j) y T* 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。 tvb now,tvbnow,bttvb* J% H) m! O5 X* _' {8 K
" @2 _% a! [* 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。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.
- v$ E/ S7 O* C; j: L1 b/ n5.39.217.77:8898A 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 & I# | I% X8 r* b3 t) W
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,
: A1 t% P+ O- p: Z; ?tvb now,tvbnow,bttvbcausing avalanches of debris into the crater. |