One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
" G8 C- A9 P+ W公仔箱論壇eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
" c, Y; z% {# qactive each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
$ n5 z1 }6 f, G3 x. ]1 \Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 3 n3 Q! z. x( m) y5 V3 r! s
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 公仔箱論壇 t5 ^) V. ?; L- G9 f
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
2 K9 [9 T4 ?4 @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。They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
0 ?: [! L# k' i& S& hof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
2 k: Q3 Z) j4 G' r公仔箱論壇taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash tvb now,tvbnow,bttvb/ @+ C3 r* B k# K( f* j4 X
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 tvb now,tvbnow,bttvb1 s0 o: ^0 i4 g9 r7 X! e
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
) y8 j# w" w: I& s2 k. e6 Ytvb now,tvbnow,bttvbyears. The island’s jagged edges were created by massive avalanches.公仔箱論壇 H- |) t, @1 {, a ?4 x2 c* i. |& v1 o
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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
2 R2 R7 u& E1 W3 n3 |7 L' Tof Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet 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。" S" m; o0 h7 B8 r: _) F5 o) ^3 G8 I
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of , c) e9 | Y# ~1 B# |: ~, O8 t
the continental crust, creating magma that drives the volcanic eruptions
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, Y8 Y2 A1 z' s- G0 f8 ?% o+ } jAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano 5.39.217.770 X4 h/ V# G" ?7 ^
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 & g6 M. ~$ Q0 N 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 ' i. Y" q3 C4 f4 m/ i4 [" M' C
as 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:
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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.
# }6 B* r; x. G( A1 ~" [0 { * A shockwave from the eruption could have blown a hole in the cloud deck.
+ y$ U, C' Y* Q: A! J, Q" 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。 * 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。* O/ [' R; r- {) x8 U1 \! ^
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
& y j' \- [5 S% \! A公仔箱論壇It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
5 z, T9 m9 R! K; n: }' atvb now,tvbnow,bttvb the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.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。1 C9 _6 g6 o& e4 ~& 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.
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! O, t6 g! X0 B( G* o! u& xMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in8 N4 _& ]7 O4 C! A5 e" U3 e" G$ r
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 5.39.217.779 A" y9 k: `2 a! u
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
2 c* t0 A1 y Q+ i& l" B1 {) }公仔箱論壇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 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。- e0 k" V+ Y+ x8 T6 T' S
also be the oldest-known active volcano.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。& F9 v! Y1 W- ?1 L% A' q
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" d# W# O1 ~2 d$ y4 i: C" u% h5.39.217.77A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high 5.39.217.77+ n2 a2 H2 B0 b- P6 ~' H
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" t" i" W/ [2 k4 b* c
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& X' \& X$ k7 q# s! T9 N5.39.217.77Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
: l2 Y& X+ m$ [tvb now,tvbnow,bttvbThe 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 5.39.217.77$ @$ @9 r% v) L" L; _2 n
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 tvb now,tvbnow,bttvb7 a) Z2 o" u. X1 P+ k \
of frequent activity. The plume reached heights of around 30,000 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。( k% k8 G5 Q8 ], _
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 7 S& P8 g; u3 F t$ {+ E: j
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate. E9 ?8 X: q6 A9 D
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Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic + F! r9 q" m9 C* P' M- g
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.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。& z( F6 O$ q4 ], X
# |8 i4 b0 M) G% ~- b. X* b5 j1 z tvb now,tvbnow,bttvb' X+ T. w) }/ [9 b+ Z0 t
- x4 Y% }+ k' p! i2 X" x. S% \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。This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
8 q! K4 c& f* U( ~0 @7 X n2 A公仔箱論壇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
* D1 y$ q- A) w b0 U @4 s公仔箱論壇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
6 I5 l0 B) N- d8 C0 I" gstationary 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.
! Y. }5 c- G; P! N4 }1 pTVBNOW 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 9 J6 b0 t" z/ P8 |9 ~8 R
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。2 [5 W# q$ r) K
causing avalanches of debris into the crater. |