One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
% O2 y9 W5 {. X& Y. |/ u; \tvb now,tvbnow,bttvberuptions. 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。+ k! @/ d3 y1 m7 g/ J
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.2 [. }0 w. I. ^" T
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 5.39.217.762 L* A/ ~8 |& V6 ^
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
$ x1 N; b1 |9 ]# _( `7 Rtvb now,tvbnow,bttvband explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
; p9 K. y+ L8 u" `/ 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。They 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
' Q7 t, Q) ^" u, N8 m+ t7 }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。of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas( d1 ^- h( r; i' d2 \4 T1 q7 p; ^$ B
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash $ M+ w7 t* e! w, [$ `
plume reached as high as 50,000 feet.8 s0 F+ Z- y) d" |
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* \) l8 F) v x+ lAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 7 c& u) `4 [0 C" E, y- d6 {
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6 o- m4 j$ w! \& x
years. The island’s jagged edges were created by massive avalanches.tvb now,tvbnow,bttvb+ Z! l e6 q. d. F) i v, F; r( u
) D( o4 a: N* h) uAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
; E3 _6 C: J. U6 Pof Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet tvb now,tvbnow,bttvb+ o1 ^8 h8 b: T1 b; v4 P& D
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of 5.39.217.769 B/ @( D- W M$ l* d# Q* H
the continental crust, creating magma that drives the volcanic eruptions5.39.217.766 s6 z* l& ~1 C/ z U
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9 A5 M' u( x; M9 TAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano # ~3 R, E( n N( Q& W
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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2 m$ H9 a1 P5 ] Q' hThe smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
& i! X3 n( w1 u$ n% g: n3 Y5.39.217.76and 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
; O: V4 b+ \( Oas a pyroclastic flow.公仔箱論壇! i, [' a, @! b8 `8 u+ _- O' h
( }' } M2 c, i4 a* p3 UThis 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.
. q3 g+ L* ?1 L' i% s& n5.39.217.76 * A shockwave from the eruption could have blown a hole in the cloud deck.
# }/ t: _) V; N5 J0 W6 W/ h; Q * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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0 i; R) D; ^3 |. ~4 U! q" CAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. 公仔箱論壇. J% n c" z* \8 p1 u, g
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when5 Q, m' n5 A/ Q6 c& P
the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.
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' O5 B/ b! Y9 k- B( H" D( h2 I公仔箱論壇Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.7 n4 f8 ~; x+ U) w" b9 B
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1 n5 @/ T/ b6 E* U% n8 y. f公仔箱論壇Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
* `7 M* w- l3 j5.39.217.76 the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 5.39.217.76( C' Q9 E) C4 x( q- w
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
1 g& N0 N2 F- p6 ~6 m* mthis picture are from forest fires ignited by lava.5 f5 O' ]) q% R0 d( D" @. A1 C
6 G( G5 E( l/ M( A. u7 i: Z% Rtvb now,tvbnow,bttvbEtna 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 ]3 G) r( V1 L
also be the oldest-known active volcano.
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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。# U; H: v# e e2 r* t; U
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。8 K* g7 K1 K9 j& U8 v, n2 L
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.' I& W, y7 `' n
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! {# r1 v* G- n3 B$ P: LPopoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 5.39.217.76# x& j5 j$ u/ e1 ?7 @; T f* O
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
( E: l% [& R/ vtvb now,tvbnow,bttvbmultiple 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 5.39.217.76. M) ~7 ?- T% X' D% c, J
of 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 - i) w | ~8 N5 N9 e: I- ?
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.7 O/ D2 E* b% L- ?4 ]
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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 5.39.217.768 @* b. _" T: u) ^& E; _
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.
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* {5 d t& j" H6 ^This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra tvb now,tvbnow,bttvb9 P$ m7 c6 d! c& l, {
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 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。" b+ i1 d2 r4 |8 j3 O
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 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。" z H, f+ r$ [$ M! U- E- ?
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.5.39.217.762 g& t3 \1 q# s* `1 ]
- A2 U' z$ ~7 m公仔箱論壇 公仔箱論壇4 `8 f1 x$ u9 i+ o' I9 C- `
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。% X5 F. K: e+ ^
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. 5.39.217.76; I$ ]% g" o. }* m% ?
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
! Q6 w. x! ^% U* m) Z6 |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,
) L) ?: ~: ?, q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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