One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 公仔箱論壇5 S( t3 s. a/ ^* g2 L
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are ) h$ n, `* O* n: r y& k
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.' b8 u* v- k: |0 v& F0 m7 V" x3 A; ], W
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, tvb now,tvbnow,bttvb J% i1 U. d. P8 s v- j
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous : H* A# Z, m! G) N: c1 ]
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. / s7 b3 _: O) `' |7 Y1 I
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.www.tvboxnow.com+ r& W' L+ R3 e7 l
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
# W# ?$ \0 ^/ j, Qof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
. q! u* [9 v0 a- I/ K: Stvb now,tvbnow,bttvbtaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
; r0 K% \. S7 r' e+ T7 f+ vwww.tvboxnow.complume reached as high as 50,000 feet.
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0 w. i$ a' P8 d0 E( D公仔箱論壇Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra www.tvboxnow.com, s9 O, p8 ?6 k( {7 `$ 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- y k! x5 q0 R2 X0 _tvb now,tvbnow,bttvbyears. The island’s jagged edges were created by massive avalanches.
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* t0 Q p3 Y2 Ztvb now,tvbnow,bttvbAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
0 I& Y* R/ ?3 }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。of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet 4 ^! Z5 C8 D0 T2 c2 c
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
* o( {2 `+ D) z8 A/ j: Q+ n5 d公仔箱論壇the continental crust, creating magma that drives the volcanic eruptions
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
; ]' K3 J9 Z# \- Rwww.tvboxnow.comin the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years., ~, w6 K, }& k2 g
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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
3 P9 P' u: Q* C6 d+ `6 d7 @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+ U0 N2 C# }! qas 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: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。( N9 N8 T# ]! s3 m! b+ ^" m5 {
0 Z$ R3 ` N$ Y/ L/ i公仔箱論壇 * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
8 u, A& J- G# k( 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。 * A shockwave from the eruption could have blown a hole in the cloud deck.公仔箱論壇* V5 C2 G! s6 E: ?4 u& b
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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0 }- _8 ?4 K, ^. \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。Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
. o, B) |9 t' F* ], Ztvb now,tvbnow,bttvbIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when2 [$ M; q U' ~$ w9 o0 M; P
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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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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Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
8 U( w% j) c3 ]( b the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
2 \ x! I* E2 ~2 I: g/ w3 BTVBNOW 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 1 Q6 \- I7 p1 }* I$ D& `
this picture are from forest fires ignited by lava.
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) ~2 {. U7 M1 O/ Z& F1 D9 otvb now,tvbnow,bttvbEtna 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- \, \/ @3 \! J/ X% t& D" l
also be the oldest-known active volcano.www.tvboxnow.com1 z3 R8 t4 Y( S9 g# \. f7 A
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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
& K! R: U$ ^8 S% G/ `, wand 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% L3 ^* H: J- \) U8 s' [
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. tvb now,tvbnow,bttvb6 [ Y6 N8 {2 l: B: [1 m5 c* 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
" r" I6 G T5 W+ `% Z( ltvb now,tvbnow,bttvbmultiple 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 www.tvboxnow.com2 U# t0 X( u3 |) m% E
of frequent activity. The plume reached heights of around 30,000 feet.
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
% o$ s3 ~- T* L# z) Z \/ Z4 iwest coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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8 a; k3 y9 u# j7 [" p公仔箱論壇Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic www.tvboxnow.com9 y5 g, K3 o1 G9 R5 ~5 c
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.公仔箱論壇0 a# ]: m* W2 F. W* c
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3 L* O/ i" w; |/ H! swww.tvboxnow.comThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra $ t+ f& D: B" g( C3 \
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 2 l$ x5 E5 @$ j* p
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
7 Y# I- g# @+ V" tTVBNOW 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。stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.1 @3 }- |$ ]3 @) f& t. I- _
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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.
: L) A T. F, h5 I5 l4 i. }tvb now,tvbnow,bttvbA 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。! ~2 e% u; K5 P2 ` }/ y
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,
# r" h7 c9 i9 i% }2 Ctvb now,tvbnow,bttvbcausing avalanches of debris into the crater. |