One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
+ W( w+ D* E2 L2 g( c. U' ] g8 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。eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are - i$ Z: Y7 S; J( I
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
+ E6 A2 Z2 ?7 D0 {& T公仔箱論壇Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 8 ^. Q g! H, {% J
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
5 h: S5 L) m* i! Hand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 6 |' e6 V7 n7 m4 N& X4 e1 [- a
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.tvb now,tvbnow,bttvb V I7 x) F: ~8 k( {
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
0 o1 f9 o. M; }7 Dof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas0 O1 z7 }# N6 k3 ]) W# ?
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
+ d; [4 ?- Q1 \2 Z4 D* zTVBNOW 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。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
- h, {# c. X7 Qtvb now,tvbnow,bttvbsatellite 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4 W) T1 \- u6 ~, `9 o1 l
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 tvb now,tvbnow,bttvb- }8 J$ } \! g8 U9 n
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet 5.39.217.77:8898+ o. u# ^, j3 w/ {% `8 ]
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of tvb now,tvbnow,bttvb% O7 S& K( c' H" q& H& t
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 % I3 W. `* j, w7 {. g
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.- C- Y8 i4 V% t& h( Q: E
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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
0 m" }% W* r+ I8 Pand 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 tvb now,tvbnow,bttvb' e% b" D( p1 Y2 b3 j8 S
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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, ^4 f$ r/ o& [# _! w& v5 n N * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
, n# p: i& X* H# I/ }& @ * A shockwave from the eruption could have blown a hole in the cloud deck.
" z( I; p5 B# v6 f5 k/ K * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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9 V$ @6 |: C, O) g. V6 ttvb now,tvbnow,bttvbAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. 1 U3 M0 p, c1 M: j
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 whentvb now,tvbnow,bttvb% h: d6 _- W2 Y# [
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。% Y' v4 h" a6 K1 _9 _; r
, i/ ^6 C! y" @" wRedoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.; Z* [7 K' M ~; {5 R$ l5 `
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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 in0 s* c1 Q, F9 I0 h. }, @$ J9 {
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 s: W: V2 p3 U+ M
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
' @1 A$ K9 X! V5 l, V$ R; |公仔箱論壇this picture are from forest fires ignited by lava.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。4 k0 D9 V, S, S& f: s9 b
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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 may6 K: s& U% N+ T, ^$ r* P
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
9 G' w% S0 n$ {* N) r4 `0 B- RTVBNOW 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。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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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
/ X0 z+ U# f5 g5 z+ U2 `% PThe 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 T) S2 J( T% I" K$ ~
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
" r: f6 B( c$ I& M8 i4 vtvb now,tvbnow,bttvbof frequent activity. The plume reached heights of around 30,000 feet.5.39.217.77:88986 U" K0 m! O$ s1 j7 \! U8 R
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) x( g: t o+ T4 \5 @/ W4 TThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the " e4 U1 P' x Q3 c
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 n! ?- T3 N+ @; f, {* R8 D" H
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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 ( m7 c- [& e' H S" o) c2 l) l
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.tvb now,tvbnow,bttvb! n% w; }: _+ o; {/ C6 b+ V
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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
: x8 V4 Q# U1 Q% L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 5.39.217.77:88982 P+ L- k( T: O& u
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 5.39.217.77:8898$ V2 p6 r7 p k2 W$ t1 t% B5 i F
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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1 A2 p$ L+ [! X2 l2 _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。
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8 S7 O5 a2 ~+ @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。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. : f$ P5 d' b/ W+ X/ ?0 A( S; H
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
[8 x3 V3 ]! c6 _4 D5 D% i& y3 ?tvb now,tvbnow,bttvbthat 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,
8 o; s5 A$ x+ p; K- T. `3 `tvb now,tvbnow,bttvbcausing avalanches of debris into the crater. |