One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 3 N6 T# U9 f4 M% A5 a
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
" S% R7 u- M( k" Uactive each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.+ T' h6 o2 L& ^6 y8 @ w4 T
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
% t6 Z* R3 o5 F. perupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
# b* q6 d- k, Z7 Z, kand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 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。) f$ W" F8 G2 \7 i' h
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.! c4 I" ?1 Y0 j; C! J9 N$ y
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9 w* q% S+ r( ^) i' I5.39.217.76Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
, o- m- F- z$ N5.39.217.76of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
0 w8 b- W# h! h$ R0 Ytaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
' P' t0 B& }! jplume reached as high as 50,000 feet.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 H0 U& R! n- a) Z
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra L5 |2 |7 B1 \# f
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 . I0 Z( y0 N5 c; g
years. The island’s jagged edges were created by massive avalanches./ Z1 {! B/ D/ o+ @/ {! @: Y0 x
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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 公仔箱論壇, v# j3 C6 B' z1 X
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
) ~" h6 S" P! G& U, oocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of tvb now,tvbnow,bttvb4 [# E- o8 M: Z0 I
the continental crust, creating magma that drives the volcanic eruptionsTVBNOW 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。$ S1 N# L7 t% O
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano 5.39.217.76( _ d7 z: c$ L; F, ~
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.1 y' q7 _- ^. o) {3 f4 T% Z3 I% ?
5 @5 z2 b$ n0 }. H; J3 }2 F9 Z5.39.217.76The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
_1 _8 T: T1 @9 e" K0 @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
$ Y) M) @3 _' G! e# htvb now,tvbnow,bttvbas a pyroclastic flow.
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- J' r$ M1 g+ |) I+ }# d2 I+ A5.39.217.76This photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:5.39.217.76. h' Z/ A" T3 j6 I' q n
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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.
% G6 b5 ?$ h- l. c: v& r公仔箱論壇 * A shockwave from the eruption could have blown a hole in the cloud deck.5.39.217.76! Y) ]( o# h* F- M; L( j
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.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 s/ X% e! n) {: ]& \# P2 P3 j
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
; N" R! r* ?3 d3 H/ ?5 L' Q5.39.217.76It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when4 [) V+ i; X0 Z( F1 h
the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.1 u w* ^; R. [! \/ B
) M8 P0 A* z. n- uRedoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.3 s6 {: `; e5 M9 t" d- f
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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
$ J6 A2 W8 p7 |6 J% g the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
, s# F& @ m7 i6 | O' P5.39.217.76captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in 3 m, k8 _+ ^9 L$ d( m! F1 V" a
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
/ d7 V ?+ x' h& G* C; ^also be the oldest-known active volcano.
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! Z7 a5 i) C1 @; ]+ L% ]3 }4 m5.39.217.76A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high 5.39.217.765 [. h" ]( X3 ?, L" E- \1 x8 T
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.tvb now,tvbnow,bttvb! h8 L* ?: b2 U- V
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, Z: M. D/ e! y8 i! _: n0 lTVBNOW 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。
: M0 L! T U# [2 B$ OPopoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
8 R5 [- \3 ?& O* u% p# B$ G+ D5.39.217.76The 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 ! _1 T2 Q g! c+ ~5 w- b
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
0 l) g+ e$ m$ k, O- z, g H公仔箱論壇of frequent activity. The plume reached heights of around 30,000 feet.
; e8 g9 u% `9 ]# ~& [" f公仔箱論壇- r6 m1 \8 Z n* U) m* t. e9 S" i
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& J0 ~1 C# @0 @* y8 i% v7 RTVBNOW 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
, N( x6 @9 {& y+ v" s公仔箱論壇west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.5 k. M: M" a* l& g0 J0 n" [
6 ^5 m8 D) @3 C8 i- ]5 a" {Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
7 {+ b; e$ } p% _' D$ g- N4 R5.39.217.76flows 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.公仔箱論壇& X3 X7 b4 T, v5 Z
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, C! K! V; U% e& AThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra tvb now,tvbnow,bttvb: D; }/ p5 ^5 L+ B3 U" t* ^7 S
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 tvb now,tvbnow,bttvb, e; l+ r2 v+ Q7 D8 a6 g
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
* j1 j0 N9 y# @5 v% |2 I4 b3 O9 Ustationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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1 B9 ~: f `5 `, Q9 V0 s7 FNASA’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.
+ I0 ?# F9 Q; ~+ PA 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 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。' I/ |' g) i+ ^
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,
3 H8 p# R, N$ `$ {$ y5.39.217.76causing avalanches of debris into the crater. |