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。4 |2 i' e, ?/ h, K' m
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
2 E6 n5 O2 O* W" Hactive each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.& C; i* V$ n( S" `3 i6 z( G2 m
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, : [/ e3 A9 C6 N0 n7 F
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
n5 X. Z2 g) M4 ~; m公仔箱論壇and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 公仔箱論壇/ e3 S* A% a" }0 z6 x
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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" i2 S1 b4 C5 i" z' v" ?' K xMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
' }! R4 D* T7 a, Z: h! o$ vtvb now,tvbnow,bttvbof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
~/ E+ o. h1 ^7 Itaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash 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。3 R2 Q. G7 O0 m9 B) Y( ^
plume reached as high as 50,000 feet.公仔箱論壇* x o9 y7 W9 i3 v6 i J* M+ b2 i
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! o- T) |8 R1 o% n! KAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 6 K! Z: O, @7 q- X8 W7 n# X
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
# b Z$ }, z$ d5 y+ v公仔箱論壇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 5.39.217.77:8898* U( \" M8 o; Z
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
: M8 t D. ~$ X! g4 W5.39.217.77:8898ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
n1 K) f+ R1 N! n7 o5.39.217.77:8898the continental crust, creating magma that drives the volcanic eruptions
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. u5 w5 h% L) F6 y2 V; N& qAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
3 R) t1 \% y+ K; 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.
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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 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, \7 T" M* m4 M+ w1 W% o+ A
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
6 M+ N9 r6 U: w: F0 J0 O5.39.217.77:8898as 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:& j* U( C% O( R- O- {! u6 X5 ?6 h
: ~9 n6 Z5 R8 ^) T' E' z5.39.217.77:8898 * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island./ J1 U/ R3 F0 L% y+ @( X
* A shockwave from the eruption could have blown a hole in the cloud deck.
" }( ?! C* z* P公仔箱論壇 * 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.
; j6 v) ]( D& \1 L. I5 o9 b: t5.39.217.77:8898It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when公仔箱論壇8 [$ `1 x4 M7 o( p# s/ Z& M
the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.6 z: u8 N5 b- G0 S" o+ l
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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.5.39.217.77:8898: f, E. |9 Z6 B4 P/ m e8 e5 F
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tvb now,tvbnow,bttvb. {' a' h I; i" b6 w7 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
+ ^! }) K+ `" m0 `$ M8 C公仔箱論壇 the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
' f# [ ^) ^! d- H; {公仔箱論壇captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
2 F" F% s2 b9 q9 _5 A2 t6 E! jthis picture are from forest fires ignited by lava.. V1 d2 Y4 @( Y' _
" b3 B3 D( v# D公仔箱論壇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公仔箱論壇 I/ h! o9 Q- W3 y6 ~
also be the oldest-known active volcano.3 ~6 F6 P3 g8 Z
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; S( E# F" n0 M7 I$ \. |5.39.217.77:8898A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
9 }# \0 Y# s8 f" s7 @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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9 M' r5 I( X3 Ctvb now,tvbnow,bttvbPopoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
1 G [' T# Q; G& q U4 m% ~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
( [: w- C8 r) e' d5.39.217.77:8898multiple 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
6 \3 {- J8 n/ C4 C4 Mof frequent activity. The plume reached heights of around 30,000 feet.
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3 S2 g; s* o7 c; B* D$ J# jThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
' L& ^* c7 {+ ewest coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.5.39.217.77:8898% p8 a( T" y. z$ y! R, n( C* j& Z
! I9 f6 u) Q9 E6 p) l$ RChaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
. T9 h1 C A. B' P7 bflows 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
. T2 p: O1 s' l" j! B3 ntvb now,tvbnow,bttvbis 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 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。" R/ ^; z* \, X5 o0 i; Z
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
) ]) D* [! Y( E! R& p. D: p) U5 Mstationary 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.
3 E$ J9 V. T T8 R7 b' 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。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
. s6 t. r0 f( }% r2 c! pthat 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,
. b9 F/ p) { }( B, L公仔箱論壇causing avalanches of debris into the crater. |