One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic tvb now,tvbnow,bttvb& y! z- x- {. ~
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 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 p( R* V/ @% R# \6 r
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
6 o2 o7 t. P3 n9 YTVBNOW 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。Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
) f0 M6 i* U' E9 P2 |, d5.39.217.76erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
+ |7 ~$ M/ M& ~5 f5.39.217.76and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
3 c2 B; j# q, i" }. U( otvb now,tvbnow,bttvbThey tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.5.39.217.761 s' @4 a1 Z& c& U! s
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5 Z1 l' H6 d- n; t5.39.217.76Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
- \ ? Q+ T( c3 N' S公仔箱論壇of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
+ {" p0 p- g6 W+ c5.39.217.76taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
3 w. E, q( h( n6 _: s6 [2 ]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。+ A0 D+ b( B; [! s5 a
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% S9 j0 v" u1 f2 x8 W5.39.217.76Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
3 ~0 @9 }& A, `; D5.39.217.76satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
+ E- I: }7 c; V( I, uyears. 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
+ M. w4 A: }0 B4 B* e公仔箱論壇of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet 3 h. q3 Q' f9 v' f0 v+ l; e- v ~
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
* u: P7 j+ d' i- Q: m; @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。the continental crust, creating magma that drives the volcanic eruptions4 y0 v* e1 c4 t/ i' e6 H+ d
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev 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。! r- ]$ m3 v* O* O: r) `# n/ D& u
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 tvb now,tvbnow,bttvb/ B' `* h8 g5 M' z5 G9 S! I: j
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
% n' [( {3 H7 m) q) z公仔箱論壇as a pyroclastic flow.tvb now,tvbnow,bttvb8 {0 v! x' R, ?% G# M
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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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8 K0 Z' H4 Z" ^! ?7 T* J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. H7 A7 V: l4 g0 t4 E( M" s& @
* A shockwave from the eruption could have blown a hole in the cloud deck.tvb now,tvbnow,bttvb- n0 m! n3 p( @' \+ P# [1 X e
* 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。* J- _6 \3 C2 m+ m; h: {0 U
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tvb now,tvbnow,bttvb$ I2 ?/ \6 X: ]
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
; J* W" S- _ w, MTVBNOW 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。It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when8 M) \; ^% Q& n2 X6 v
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9 \/ i/ U$ p8 @8 K, A( I
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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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% H ^+ z7 s, F% U) A9 b7 [ oMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes inTVBNOW 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 V9 T# i1 b9 M: R/ r+ D3 X
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 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 x0 x1 r1 q# ^' H
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in tvb now,tvbnow,bttvb5 ?2 n8 ~7 t' g2 K
this picture are from forest fires ignited by lava.2 _, I$ O' C6 j, j5 U2 G: p* _" Z
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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
0 i: I8 R m9 j g% Q7 DTVBNOW 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。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。/ |: G5 f" z7 { ] x
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5 }3 `) [) T7 z4 X. XTVBNOW 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。公仔箱論壇; ]4 C% |0 p! B: T7 ]
A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
/ n8 O) P$ e4 b) l. C3 y2 Q) |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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' V, c) K0 h% ~& Rtvb now,tvbnow,bttvb 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 u5 H9 @1 B; H4 n: J, y
" H2 e+ D8 K+ ]3 r+ T( r! P6 y6 DTVBNOW 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。Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 2 W/ u. u w: q8 L7 Z7 m* r' i
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 * z. W2 \6 U5 \# Q6 }- i9 D
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
! X& o# Z! N8 L; T: Pof frequent activity. The plume reached heights of around 30,000 feet.
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- i0 O. Y/ u4 \9 D$ A5 XThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the ( F/ |: L3 u' Z R F" [9 ^
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.公仔箱論壇# x# e- {6 m" {! r# _" ~' x
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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
/ V. F( @3 Z* P8 i- f) a9 Eflows 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 2 e3 v1 J8 L, V
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 tvb now,tvbnow,bttvb% D2 Y3 ~! s8 C% T
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
c" G8 {+ Q+ a2 ~tvb now,tvbnow,bttvbstationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.公仔箱論壇0 k7 W% n& S( C9 g* Y A. ~
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' V: L! }8 q2 H. E0 O6 k+ \- v1 _5.39.217.76NASA’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. 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 J$ i5 f$ x6 z5 E8 E6 e
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
+ [6 j' {% N9 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。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,
5 j: K8 G' K( c. g7 N公仔箱論壇causing avalanches of debris into the crater. |