One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 公仔箱論壇9 O" q3 w" a/ H! J( x
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are ' H# x. l$ [$ g" E2 |) @ D2 b
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
( e; u' H# K+ x$ S9 Q6 Y- E) t1 d5.39.217.77Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, ) d; p( |; f5 s
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous V, j) B: }2 ~" p
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
3 k: C0 F# X, C! T3 e [7 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。They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.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。: T$ i1 ]0 C# Y! O9 Q
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above - S4 M! N" m' `: }
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
5 A' x: M9 B/ d' _5 Ttaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
$ z4 L I4 F% g; Y8 @tvb now,tvbnow,bttvbplume reached as high as 50,000 feet.
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1 o& ?- j7 A+ n1 [Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 5.39.217.77! h" T. z" `2 ^) F1 m% h. ^
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
( M+ ?; D0 E5 b' \5.39.217.77years. The island’s jagged edges were created by massive avalanches.; D0 S' _, C2 s4 B1 r4 `; Y* ]
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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' [* n( H0 C/ G- e! R5 h
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
5 P& R7 ]/ o5 L S+ pocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
5 c( K3 t! v: E J公仔箱論壇the continental crust, creating magma that drives the volcanic eruptionstvb now,tvbnow,bttvb& a# P1 }- m0 _
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano 5.39.217.775 e4 w: z# v- ?% j0 u4 ]9 S7 T5 H7 u# J
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
9 G* n' `) y r# Htvb now,tvbnow,bttvband 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 ( s' j+ {# V% o8 j, M
as a pyroclastic flow.
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* h: ` b1 A4 k1 [5 wThis 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.
; G9 t: a% c) C; x- W+ v1 H * A shockwave from the eruption could have blown a hole in the cloud deck.
3 N( }- {2 F5 Y0 ^2 C$ y i * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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2 Q+ B' C& ^9 C8 K- s- g3 Wtvb now,tvbnow,bttvbAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
4 R, h5 I5 b, ]) ?5 ^0 E. S$ 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。It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when公仔箱論壇5 @( r# Q! Y% S7 x. C! x/ b
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.7 r/ n* |# u: \# j: m& f& T+ K& T# Q
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C& \9 B8 R& E& m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 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。% X+ D* }9 u+ l! |* V' U
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
' i) E6 c! ]& Q2 [+ N8 r5.39.217.77captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in tvb now,tvbnow,bttvb, c- R$ t, c( d: H' f
this picture are from forest fires ignited by lava.
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" u% U" h% }; U r% r9 b, m; k公仔箱論壇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/ x2 _! X* y* P; R" T/ B! _. [. 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 m% J2 n1 M7 O, n0 j
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.
4 d% |( }$ M# m, d% ?6 mTVBNOW 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。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。7 `5 `' z+ i4 k' y, P* {
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
3 o4 p& R# I' g, {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 3 m4 {& y. T; o
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
( ~/ _. I7 I" i5.39.217.77of frequent activity. The plume reached heights of around 30,000 feet.# d% ^) N4 C1 q2 T- d7 `
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a1 p; k+ d/ W+ B4 dtvb now,tvbnow,bttvbThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the tvb now,tvbnow,bttvb. J) y* \4 ?: O3 e P; v
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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, I& Q5 w3 M5 u3 ?* h0 h) ~tvb now,tvbnow,bttvbChaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
# u- l1 H/ ` C3 N公仔箱論壇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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4 `4 o1 F6 w, f; s2 A0 W; `3 N5.39.217.77This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
2 Z, F9 L7 K* \# D, x3 `; mtvb 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 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。$ ~5 x) x2 w8 C! M" U6 J5 _: e9 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
- z8 w2 |, n, @2 L4 E5.39.217.77stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.# a, k2 ^' h9 _7 J o
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+ p2 R }. Y5 L, i: KNASA’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.
6 F2 A8 e7 j! bA 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 公仔箱論壇, D) q5 J1 `% b# f+ x
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,
% j8 Z' o. `% w: r8 e- i0 V) v4 F5.39.217.77causing avalanches of debris into the crater. |