One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
: G; v5 r% I! y3 iTVBNOW 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 5.39.217.77:8898/ q5 Z t7 X+ W# I! T% U
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.) k4 s; }5 R0 E9 t# L& `$ z# S$ Z
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
" o; @ Y2 F% b r& W; Ctvb now,tvbnow,bttvberupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 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。- [# ~ Q$ X4 Q2 L7 a! j
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
: E, M' f0 J, S& K公仔箱論壇They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.5.39.217.77:8898. X* G# u0 G+ h/ [0 \: s; ^
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 3 ~! V$ o8 ~* y. Y* N2 }( o# ^: g
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
! c- |, K, Q, f: M1 t9 b' C$ {taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
) L, A' i/ W; P, `2 hplume reached as high as 50,000 feet.9 ]) ^. \8 [9 }6 e
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: R8 F. o2 ?2 C6 R8 H4 n/ X1 w7 i' G5.39.217.77:8898Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
3 F0 j! K* k' N. K* r* ]* G, h5.39.217.77:8898satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 5.39.217.77:88987 B% u! m' @3 v
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# r6 X2 C$ n. @/ d9 C
of 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。( |6 H* p+ x3 {& O
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of 1 O! f/ i/ S# _; F' \
the continental crust, creating magma that drives the volcanic eruptions2 u# v" E$ t" G/ }. U
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% S M1 f& T% ~) ^ @& KAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
1 y6 B' ]% d+ Rin the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.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。% m8 n5 M Z) Q. k3 d% O4 m
1 X. i6 X2 e- _' t, O# l' X4 `& ^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。 {; [; T' A1 o. `8 ^" _
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 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 D* ~5 I! t5 k% k
as a pyroclastic flow.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。8 v+ u' @& D+ n$ V4 h
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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。6 f4 t, G. ?; M
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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.
* Z) d* O2 f' B4 M+ X2 w公仔箱論壇 * A shockwave from the eruption could have blown a hole in the cloud deck.1 Q: Q+ j& q$ s4 E
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.1 @! ?( {* K# H- D( R1 m
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8 \) q& u) O& g9 h" B7 M公仔箱論壇Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. 7 f8 E0 i. ^& s. C% \ ~0 ?* K5 X% n1 m
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
! w- R! x. y( h$ ~公仔箱論壇 the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.; u+ o6 r& w9 d! J
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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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: U4 S! D4 W5 U. I- m5.39.217.77:8898Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
; X6 ^7 l7 t" d; f% X& ]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 - a+ q, O0 v. A8 r
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,bttvb$ y& r8 n% |3 K- L
this picture are from forest fires ignited by lava.
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$ J+ I; N) Y* O/ N5 a5 |; DEtna 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
; h% H8 o+ V# F* ]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 tvb now,tvbnow,bttvb6 z8 ]3 D6 @9 F" Y* w, _4 N
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes. x* a* I \! r5 z/ ?; y+ p$ J8 T
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
a6 I) O* i# K/ G4 a: Ktvb 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 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。% Y& N& \$ f0 { [0 z+ o6 |8 |
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
8 X4 z7 G* u8 d4 cof 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 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 g' s: m( s8 X u: q: ?
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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, p# c& [* Z# n' X g' P! t" Htvb 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
/ s; U: o- `6 g# c3 N8 Lflows 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.5.39.217.77:8898- Q9 f. N, T1 I9 F
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9 Y5 `. [) g% r+ \% y5.39.217.77:8898
- P9 Q' h1 O/ 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。This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra . [. h+ K% t' a+ Y; D
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+ g5 e# Q9 m' N) F. V- B1 v1 B6 u# W7 h
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
! a" e& H! g' i; a: `stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.公仔箱論壇+ o4 L4 h. J$ P: W/ P: V
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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.
0 g- h6 X( v. i9 @5 L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 $ o' L0 Z# w2 r" I' D% v$ Y% I
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, 6 R7 N2 H" U6 d( q
causing avalanches of debris into the crater. |