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。# t, @/ A) E0 F& a' N
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 5.39.217.778 X7 Y+ j: x" f% d
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
6 E& i: _; I! F( j( y+ P! F5 ]公仔箱論壇Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, tvb now,tvbnow,bttvb1 d" ~" b% i9 X
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 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。 C5 n; e6 r" E8 ~; [$ Y: ^
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 公仔箱論壇3 U3 D1 v1 K1 f- W3 w+ X
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.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。9 ~2 u) I5 p& H$ R/ q* M
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6 i! A! x. g( w6 U' i- k公仔箱論壇Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
' m, [; _4 i6 ]2 k3 \3 _) Lof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
8 I5 J) A0 z; d% Vtaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
. [' |- Q- K2 E- g公仔箱論壇plume 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。* I, H1 r( k- r/ M0 D8 a' V
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
4 @" d0 S$ K3 Osatellite 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。7 l# s' |$ O: `
years. The island’s jagged edges were created by massive avalanches.
: g9 |0 U: S4 E0 i9 nTVBNOW 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。
; L; y+ Q: `* K0 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。Augustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring ! W% [2 @( p2 t! {0 E' R1 x) E
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
/ F# P* ~* ?0 l U8 s9 z1 Utvb now,tvbnow,bttvbocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of : z1 u% e7 u& ~: R0 {) |: D& {
the continental crust, creating magma that drives the volcanic eruptions
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* x' ]5 E- @6 W, N+ |公仔箱論壇Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano 公仔箱論壇 T3 n6 d% R4 n
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.
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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 $ F$ k# q# o6 |: S
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 K6 W, O4 l* i7 b; D
as a pyroclastic flow.5.39.217.77' p/ b0 G+ B/ z" Y
% s& b( K4 n3 S* m6 T; s. v; r9 eThis 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,bttvb+ j3 A2 m" a, f
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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.公仔箱論壇$ A9 y0 ~, T6 |2 B2 s x! u0 `% L) R
* A shockwave from the eruption could have blown a hole in the cloud deck.公仔箱論壇9 e) f1 c5 X4 C% z
* 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.
) [: S6 D i! D* wtvb now,tvbnow,bttvbIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
; ^% r# Y) }- D6 v5.39.217.77 the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.公仔箱論壇& F+ }6 T* P3 C
. g7 q+ I2 K7 C% @0 V5.39.217.77Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.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。9 N4 w N; A% r0 C n
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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
~' t, l2 _! t3 i1 `tvb now,tvbnow,bttvb the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 5.39.217.778 D# a) T& \2 M# U% G
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in $ e& e8 \0 s, ^& F7 ^
this picture are from forest fires ignited by lava.tvb now,tvbnow,bttvb3 }( q- N- H- u/ d
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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
- ?4 V) h" p+ n3 T. q& j( r! Q5.39.217.77also be the oldest-known active volcano.
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$ v" D( t3 \1 W8 f. Ytvb now,tvbnow,bttvbA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high * h A% J9 I( D
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.3 T( C/ q! D1 e# K8 i) A" h
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. ( R, @- `( q1 Q+ S& A
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
$ P# Q) N F7 P( w. Y2 v! Z; lmultiple 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 2 \% L" @/ b# \: s
of frequent activity. The plume reached heights of around 30,000 feet.5.39.217.771 b1 H/ z5 H! g5 j# J. e* m
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0 S8 J; M# l7 l1 [5.39.217.77This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 公仔箱論壇6 b ]/ ]( J6 N) s8 t
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.( g7 L3 @2 t& J) L. ^) C
2 n* b7 L% H3 IChaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
9 \6 d( Q4 A% l& Y6 L7 ]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.5.39.217.771 B/ v# f* J+ D/ x4 O
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& ?; r1 M# U4 e$ lThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
5 D: h# ?8 Z( Z" p! r) D- U( O5.39.217.77is 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
! a/ I L" S, j$ u: n0 G$ a' p2 S5.39.217.77formed 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 ( d/ j" o7 h! W: w# f
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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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.
( u# x, f* D( R5.39.217.77A 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 tvb now,tvbnow,bttvb8 d! y' y- Z+ A3 s
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, 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 p6 k+ B( ]# V
causing avalanches of debris into the crater. |