One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
% W3 R- B' t: \/ 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。eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are tvb now,tvbnow,bttvb# S+ }8 ~6 _0 Y# c' e* Y& g3 ?
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.tvb now,tvbnow,bttvb R! |1 ~9 P5 Y0 u
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, ' r/ H3 |* s6 e4 Y* v2 |
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
/ e& ~: m. P+ K公仔箱論壇and 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& A& G6 i& X1 z
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.公仔箱論壇( G& \5 Q+ N1 ]8 I3 }
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 8 [7 m+ P% f9 k; G" _
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas5.39.217.760 |4 a( `) |& L# ?! {! R) ]
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash & @, K: Z" o' x" f* P. C
plume reached as high as 50,000 feet.
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
- g ~; P3 J( X7 q% q2 asatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 & e+ u, }6 U9 k: B4 }+ a
years. The island’s jagged edges were created by massive avalanches.tvb now,tvbnow,bttvb _( C7 _2 N2 ]2 q2 |# R9 W# Y
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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 + J6 J$ ?- A, z7 A1 q
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet tvb now,tvbnow,bttvb9 E* u! S2 f2 m7 [8 y1 I
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
& u/ X1 \- T% R! l, n2 G1 xthe continental crust, creating magma that drives the volcanic eruptions9 N; _# Y1 {, X! @" W
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano tvb now,tvbnow,bttvb3 g3 }2 f$ l1 G8 T! S
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.tvb now,tvbnow,bttvb/ S4 X6 q, s9 E# R) l
. c$ g" j: O/ M( j6 \1 N8 z; S3 Stvb now,tvbnow,bttvbThe smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising 公仔箱論壇' T5 Y) @) _* V# P. 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
0 w! J4 }: B) K" ^" C$ `" _, fas a pyroclastic flow.5.39.217.762 M5 d7 B9 R/ r" @+ ^) e
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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:
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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.
3 s4 e* Q+ c8 w; Y5.39.217.76 * A shockwave from the eruption could have blown a hole in the cloud deck.
' [/ }8 c9 [ a/ v' a * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.3 W4 i8 H4 V& {8 a$ H9 G4 K
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. ) P* K6 d9 R; h
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when1 T' ~+ F5 @0 d
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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* K* Q4 H! D& Z# W- k4 ?公仔箱論壇Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.公仔箱論壇( X! t7 l9 d" v
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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
& ?& J3 _# R' j5 G7 H @" v the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
- p ?0 E3 X" @" |) t" 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。captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
, H, c5 _3 D, w" f; l' b0 M: [3 j% u5.39.217.76this picture are from forest fires ignited by lava.tvb now,tvbnow,bttvb8 `8 w5 N- J' e8 Q8 w% {
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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。0 J4 ?' X8 b& o# n7 b4 X( {
also be the oldest-known active volcano.
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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
: A0 x& P5 L# ctvb now,tvbnow,bttvband 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.
- { F( P4 q. a; Z2 k& \" z5.39.217.76The 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 tvb now,tvbnow,bttvb6 R `+ j7 u. w3 b" }1 T
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
9 p; N3 t6 c7 N3 {. Y6 Hof frequent activity. The plume reached heights of around 30,000 feet.公仔箱論壇( s$ s m/ _ s$ ^/ a7 r+ z( n
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
* a0 B3 i% ^4 n& h5 _west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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4 J* s0 P' l5 J; S4 D( K; j6 f" Ltvb now,tvbnow,bttvbChaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic 5 m/ C3 h9 e& U4 o4 v$ X
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
, S" `# G8 w. z5 w5 mis 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 " g6 Z5 c# q& J2 N) G1 F
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 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。' t1 V; P0 G3 ?+ b- ~) c
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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tvb now,tvbnow,bttvb7 ~* W: t7 z, j4 L
- b5 u$ ~! a( W" L; f+ FTVBNOW 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.
5 v X5 V" E: G _) l7 T5 _5 s公仔箱論壇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 tvb now,tvbnow,bttvb K$ W9 w; X% u
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,
* o s% F' [# U! r8 B: Icausing avalanches of debris into the crater. |