One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
`3 m8 `/ Y% ?. b+ J. _eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 公仔箱論壇% I0 G2 _ [/ t9 K- J
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
0 m8 c( A- j) X# k; A5 B& N; O8 H; ?/ @tvb now,tvbnow,bttvbSome volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 公仔箱論壇7 c/ ]9 G( \, o7 n5 O+ t' ^' G9 c
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。3 ~+ x" Q5 [, ^8 [" X
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. tvb now,tvbnow,bttvb& G, J7 r6 ^( x; v
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.$ v1 k4 g3 [( E$ O" v8 U
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 9 F* @8 O7 M; H2 i, k, O
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas公仔箱論壇! W! M. Q. |6 w5 ^
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
" w# \ X, I5 L# o* w' t; jtvb now,tvbnow,bttvbplume reached as high as 50,000 feet.
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9 D8 p W" @ z0 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。Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra ) \) b. t7 W; D# {8 k; a/ e2 }; U* ~
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
( M' l- q) [/ [. N9 _. OTVBNOW 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.tvb now,tvbnow,bttvb3 J* E; H, h' R' G% |5 P4 p$ h
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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
2 S, }' N0 V% s6 r( `# Lof Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
/ [9 {6 }% \9 q3 H7 H: V/ u5 }0 _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% \8 [* D M$ M4 Y' U. e9 i
the continental crust, creating magma that drives the volcanic eruptions
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9 ?2 o" N2 Y! F公仔箱論壇tvb now,tvbnow,bttvb7 j6 B3 X; b) B6 e
7 o$ r5 f8 r1 G9 n( P7 x8 }/ a" u; ^tvb now,tvbnow,bttvbAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano tvb now,tvbnow,bttvb! N/ L' W% U$ Q% r, g9 E
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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The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising tvb now,tvbnow,bttvb7 q ^0 g u0 q* F% H$ j. v" W8 W
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 tvb now,tvbnow,bttvb9 M( N" i2 N H/ v
as a pyroclastic flow.
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/ \4 w1 y1 V% {: p5 x8 lThis 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.tvb now,tvbnow,bttvb# R3 a( c4 t4 o4 o- i& r6 ?- a
* A shockwave from the eruption could have blown a hole in the cloud deck.www2.tvboxnow.com# p3 E7 q2 n3 @ K3 p% _
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.www2.tvboxnow.com- O( S2 m) t" [1 u6 `
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9 X0 P* g/ _+ \www2.tvboxnow.comAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. - Y% q( b4 X+ {+ A6 q. V5 |
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 whenTVBNOW 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 r1 m* J1 G1 U' C, p4 I, N; E
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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Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.. |( u* M/ ~( x/ z
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' Q. {# k2 F- ?7 _# pwww2.tvboxnow.comMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes inTVBNOW 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 S" {/ U+ G' I/ c) f# H
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
' `9 s$ w, s( ]! I) U/ Gtvb now,tvbnow,bttvbcaptured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
) R- O! |5 ~5 uthis picture are from forest fires ignited by lava.
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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
3 n: p4 _+ c1 g7 R3 \4 jalso be the oldest-known active volcano.
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9 O+ o0 [6 O( S, B. \- UA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
& i8 K) ?* L: Land 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.
5 d: ~$ h0 I" n! W3 G/ jwww2.tvboxnow.comThe 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 公仔箱論壇/ e9 Q( D+ s! q
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 s' r$ Q% o6 L. i3 [, [ ^+ [! ytvb now,tvbnow,bttvbof 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。9 Q, P" h( ?" \" N- g7 z
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; V1 H! k* Y# p' J, p, Uwww2.tvboxnow.comThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
7 X- R$ l: h, O5 O) x8 Y公仔箱論壇west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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3 Z6 |6 A Q1 e3 H: b2 K; Y* CChaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
4 A& K8 Z* H4 c- {tvb now,tvbnow,bttvbflows 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: }3 G9 d1 J7 o2 u4 q
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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
7 P5 ]) N3 T" @- P H4 U( Gis 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
$ }. W1 M+ q7 O5 y" ^公仔箱論壇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 tvb now,tvbnow,bttvb/ K9 Q% y) p) F
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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3 H) @# {* n' E9 T5 W8 G% `+ {( qNASA’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.
4 |7 l# ?! o6 `6 w. U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
, f+ o) x$ S2 B% _% wTVBNOW 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。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,
) ]. e, N! Q& A" S7 Ctvb now,tvbnow,bttvbcausing avalanches of debris into the crater. |