One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
" o% g7 C% G! qeruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
9 R0 O, E0 j, w' g7 @' b, I5.39.217.76active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
& A, K, ~! U k# |公仔箱論壇Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
7 d+ P0 y# s2 A/ K8 B, `% ~公仔箱論壇erupt 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。! L/ `6 |7 t' R8 K1 Y1 _! Q( _
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
$ M" F( l) t- S" Y3 Z2 Z# I2 X5.39.217.76They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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. \% Y4 e1 r/ t; C* `) H' l+ s5.39.217.76Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 5.39.217.76; c0 c$ `8 p- K4 o$ d
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas5.39.217.76; ]- `8 Q2 W, Z8 F
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
) H4 F, s$ T( c+ ^6 W+ xplume reached as high as 50,000 feet.tvb now,tvbnow,bttvb& F3 }; Y' g& `6 D! I4 f$ x( L
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 0 i; C, [$ a' S# d- N7 l
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 公仔箱論壇5 z! Z' p% N' G( U6 ]7 Q3 k# w" k
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 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。# I- g% h8 V7 y9 y5 L' A* o U
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
, v2 N" [( C6 H8 B* T. \8 X6 J8 }tvb now,tvbnow,bttvbocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
" ~6 y! m+ k% B' F% o6 R" Rtvb now,tvbnow,bttvbthe 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
" `, R5 \$ {8 ^. Z2 D公仔箱論壇in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.公仔箱論壇% _# i( \" Y( r8 R! z
# G j& \/ h, g/ }7 J0 U7 N公仔箱論壇The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
5 A9 s3 w0 C7 s, Oand 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 5.39.217.76! x' g* U7 V5 O9 x1 ^# j
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.
# `# @* g6 u, _9 c& l; n1 N7 S$ ^0 nTVBNOW 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.tvb now,tvbnow,bttvb% ?( C( v/ O- y9 F
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds./ ?) |/ M. N4 g& E
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. tvb now,tvbnow,bttvb7 G. q( o. S8 M9 |" o
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when9 q n7 z6 R! k8 C
the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.tvb now,tvbnow,bttvb' z5 V, f# G! i( 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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Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in公仔箱論壇' p$ Y% [0 O8 D" |8 b$ E, 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 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。0 |$ v2 k, H* u$ U
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
# F# Q N6 W7 I' {' K/ C; b/ O9 C& v5.39.217.76this picture are from forest fires ignited by lava.. n" M2 W4 I+ }; j. 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公仔箱論壇% @& g: m! Z2 g2 O
also be the oldest-known active volcano.tvb now,tvbnow,bttvb8 ?/ z; m; I* g0 \3 h" p
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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 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$ b, r3 P) L) j
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" g8 E8 J4 }+ e" c6 f7 S+ ?
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- h* x" p! f* }/ @& @Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. tvb now,tvbnow,bttvb' ~. s* N# g, D& G$ X: P& x
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
6 L+ O+ `7 _3 w, S; `( hTVBNOW 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。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
4 E6 x2 ]9 D8 G2 c: 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。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。- r# N6 o$ Z' }1 k" n) o' p
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the tvb now,tvbnow,bttvb6 d- \. Q, ]8 j+ o
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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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
: S) t0 a8 K$ E( c6 z5.39.217.76flows 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.tvb now,tvbnow,bttvb! H$ C2 l) @4 X: Z
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7 C) C7 P) J8 m2 J' @% Ltvb now,tvbnow,bttvbThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra " X$ Z& A! D6 M3 ?( A
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
/ n$ D0 \$ K3 K8 J) e7 ?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
+ g% `8 I/ f! d+ t" ~/ n2 j9 rtvb now,tvbnow,bttvbstationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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+ e6 J+ R) \7 {# d7 `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. 8 `9 R& C% G4 h% F( T; x
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
* b6 x1 O9 Z8 b3 A2 A; fthat 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,
) R3 D$ k# V" s8 i" t公仔箱論壇causing avalanches of debris into the crater. |