One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 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。; T4 b' X6 l' Z& m9 ]& F
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
( S( s. K6 T3 e( t8 Cactive each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.5.39.217.77:8898/ O& c: z% c( L9 r& W
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
. `3 s; {# M! g# {+ \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。erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 5 A% S) O% b( R8 z) G2 t% D+ l4 o
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
" O/ S, l, d) n4 K. \) g- _8 j; KThey 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 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 X, {1 [3 @0 F" A
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
/ | G" Z4 s# y6 Q" p8 p* y2 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。taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
' G' M8 U6 W8 dtvb now,tvbnow,bttvbplume reached as high as 50,000 feet.7 r' P* `: C0 ?3 ?" I
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 I, w: h4 {* a5 |2 d
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 5.39.217.77:8898) F! g& G' M$ L: V) t( n: ?0 B
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
# C6 |1 b' L8 v+ r4 g5 D2 F& q# 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。years. The island’s jagged edges were created by massive avalanches.2 M5 b& F" v5 l& i9 x
( U$ i9 G# `/ ^* `$ H' ~ Z [公仔箱論壇Augustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring 公仔箱論壇- ]0 } x6 V o9 W- P3 K6 @# c' m" V
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
! Q' J: o; \2 i3 j) Ktvb now,tvbnow,bttvbocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
* A& O! h3 C( m0 \the continental crust, creating magma that drives the volcanic eruptions
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$ \4 U j3 x# }) l, m9 JTVBNOW 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。Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano tvb now,tvbnow,bttvb4 A [* E! j5 P" X
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.1 Y2 [8 `% u4 k4 Y
+ u6 J/ |1 X: A5 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。The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
- L* |& _) y. L) Z; O. u6 _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。, t7 l+ a# R8 f, x
as a pyroclastic flow.
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0 G' g* j+ k' c$ k/ B$ Ytvb now,tvbnow,bttvbThis 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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, L6 b! T5 B7 P* y8 w9 Z( Htvb now,tvbnow,bttvb * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.公仔箱論壇! q( I$ B/ }9 v( ~' T
* A shockwave from the eruption could have blown a hole in the cloud deck.
8 b2 d+ I" w6 g4 W; v * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
& Z$ Y/ Q F' V* b: c3 C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 when5.39.217.77:88985 m$ |. c9 b7 `
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% W1 X4 \+ _0 V$ ^! e, q, y; D
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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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, M7 u$ r; D# _8 t, y6 w5.39.217.77:8898Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
1 S3 r) I, o2 a& Y1 i) e1 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 公仔箱論壇6 Z- ?5 L: z/ M9 A8 y( t) x
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
0 N4 O, w! t: w6 `: ETVBNOW 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 picture are from forest fires ignited by lava.
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( L; H; x3 G# \/ z8 S9 STVBNOW 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。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
5 Q$ d7 I3 w6 K! f5.39.217.77:8898also 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。, a& B3 f& U4 }
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5 T* ^: D8 y7 K8 MA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
' l) f1 R% P/ o4 S( m; t+ Z9 X- K3 xand claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.- E: d1 `- q3 j( V" a; x3 T
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" N% E9 s) G0 ~( O% A* ]; L0 Q4 X. y公仔箱論壇Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 公仔箱論壇" ^# Q4 f$ d9 |/ 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
! F b, S G5 c& Z9 e3 }# Xmultiple 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
' h C3 r& x+ S$ j* vof frequent activity. The plume reached heights of around 30,000 feet.tvb now,tvbnow,bttvb# ~" E3 n2 |) |
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8 G& E* u$ c, X! [/ U* KThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
3 [6 v! D! u, L+ A# R; Uwest coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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5 w+ z" i! ^. u1 C3 A* X3 tChaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
^/ ?4 w; @) q4 `# E5.39.217.77:8898flows 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.2 S* I, R, q( e7 J1 b
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- t2 b8 _& |( @: b9 ~% ?7 o5.39.217.77:8898This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
* Y4 \( U( w, g9 U( Ftvb now,tvbnow,bttvbis 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
# K1 `4 F5 |8 b/ V9 S& Z6 x9 Ptvb now,tvbnow,bttvbformed 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 tvb now,tvbnow,bttvb, ~7 J; Z+ {$ D6 m+ u. x# b
stationary 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. tvb now,tvbnow,bttvb+ n. g0 r F7 z, v1 t! L" a
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
- k0 q, v0 f8 x' N公仔箱論壇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,
* ^) A4 s% y% S* w3 ?公仔箱論壇causing avalanches of debris into the crater. |
發表於 2009-12-22 08:34 AM
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