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。: T* q# s1 B- E/ Z
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
/ Z" _4 M3 ?/ L# @6 H) z8 d公仔箱論壇active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
0 R& w$ R9 v c% d公仔箱論壇Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 公仔箱論壇" l$ P! V2 E) i2 }2 q7 k
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 公仔箱論壇1 U! ]. _: i& O5 U! Y6 ^1 U
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 8 w1 s: t4 ` ^; }' W# U
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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# v% i1 P% \& G% V( Otvb now,tvbnow,bttvbMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above tvb now,tvbnow,bttvb# n* d# k- I5 q9 ?- `3 i
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
x/ v3 U) R X" P) n1 u2 H, `taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
@! h+ |# x% h8 h7 v4 h" E公仔箱論壇plume reached as high as 50,000 feet.tvb now,tvbnow,bttvb& g1 f& \$ t4 j q: n; k, J
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 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 \2 g! y6 K, k" V
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
1 |4 w" P; C* H* B公仔箱論壇years. The island’s jagged edges were created by massive avalanches.5 y- e6 P! N6 Z5 B* C+ f k; n
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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
! N5 `. t' L. U! t( b" wof Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
; f6 f5 N0 |) Socean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
5 j& S3 Z8 ^5 Y% s0 U! w% a9 _tvb now,tvbnow,bttvbthe continental crust, creating magma that drives the volcanic eruptionsTVBNOW 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。2 T1 b }+ l7 S# o+ Y
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano 公仔箱論壇- p B& A3 r. F/ ~
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 5.39.217.77:8898! l7 E9 ~; ^& n3 t
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。. T8 ?) G# P8 u) b' x; C, H
as a pyroclastic flow.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。, I3 ~" b, U9 b$ Q
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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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* r& P6 [) w' g/ S2 j% |4 N) J * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
9 l% W" v1 T2 S3 @7 I* \1 d: etvb now,tvbnow,bttvb * A shockwave from the eruption could have blown a hole in the cloud deck.1 _, @% H8 W4 c V
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.tvb now,tvbnow,bttvb( \, I" I5 `/ M( [: L
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" W. o8 R& i$ ^6 ftvb now,tvbnow,bttvbAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. 公仔箱論壇( ?! R* ^3 U$ o' }
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when3 C _' [1 d' S& y
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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M* i1 j5 w+ q$ A B1 h" j8 ftvb now,tvbnow,bttvbRedoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.6 S; N! g: ~, `, Z
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# W- ~( q7 T4 Q/ K# k* }* _# v% @Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
0 I- y. I: G3 a0 q the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
) J! z0 C! j! @( Z! e$ `1 Zcaptured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in 公仔箱論壇6 M2 s, X8 W d
this picture are from forest fires ignited by lava.
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4 K4 r; N6 O, r; xEtna 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
' Q' o( {" \( H) v. J: ]also be the oldest-known active volcano.: P z# e) D; O) D- [8 H; Z
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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 ; D/ R7 w7 J g0 K
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.
; q) }: b9 J) O3 r) S# m; i c+ 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 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 tvb now,tvbnow,bttvb2 L, {- a6 i$ ^9 b* c6 U; Y0 n4 l* s
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 # d. R7 x* j4 H" v9 y3 X' E
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 1 k5 b# V R1 t/ @7 p4 P7 ~1 B
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.tvb now,tvbnow,bttvb: n8 d# }( L, n7 r5 K& S( F
" I2 A2 N$ t k" x公仔箱論壇Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
2 N+ {3 V/ w, ?+ E2 D ~( @+ I3 \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.
2 ~5 L \$ D9 |. y, 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。
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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 ; ^ t' `, h; H& q* Y0 K8 Z/ X6 w
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 5.39.217.77:88980 O2 x# c" C% C5 r% L$ ?1 M! }4 C- @
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 公仔箱論壇/ Z# z' q+ _* Z& I A7 e" P' j3 z% k
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.
7 x7 P8 A, i" k3 S; P- v$ }) Vtvb now,tvbnow,bttvbA 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 2 ^9 E5 s3 Q: A' j* k
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, 1 G0 T/ r9 o7 C8 m3 B* V
causing avalanches of debris into the crater. |