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。0 V4 r* N4 q( h4 T
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
( j. q1 u8 m5 s! P' 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。active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
! V" g/ }# N( E9 J8 B4 Ztvb now,tvbnow,bttvbSome volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, tvb now,tvbnow,bttvb! P; \% @/ D' e8 O
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
6 v% o+ }" B6 [0 [www2.tvboxnow.comand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
5 m1 f/ e; M& ?1 Ywww2.tvboxnow.comThey 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
5 n' F9 b$ m/ D0 |9 L- nwww2.tvboxnow.comof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
% v, t6 r' H! R4 d" [8 ~& P' _; Ptvb now,tvbnow,bttvbtaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
/ \, g. t% y. G3 vwww2.tvboxnow.complume reached as high as 50,000 feet." O- g) U5 ^& C B6 P2 O% @' i6 n
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! s/ Q/ e6 u8 t/ S2 A! |# a% [Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra tvb now,tvbnow,bttvb. M3 H" K: R: Q
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
$ m4 x5 h4 t3 I9 A! E% iTVBNOW 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.
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0 b% d7 S! W+ s! @. m, U& q1 jAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
- o5 n% O, {" wwww2.tvboxnow.comof Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
& g, o2 y- t6 H" a+ 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。ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
( D$ W _ b$ D) Q: ]the continental crust, creating magma that drives the volcanic eruptions
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# a, R) V) I$ W& m x; r- dwww2.tvboxnow.comAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano tvb now,tvbnow,bttvb2 h8 y' H$ [5 @& m! R6 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
" B/ t, R" G& N( N* D" x公仔箱論壇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
8 G! {& Z1 p# tas a pyroclastic flow.tvb now,tvbnow,bttvb" N9 E! T# n# o. q' H; L3 C* F
/ R$ J! W- r( z6 p. Zwww2.tvboxnow.comThis 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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; i8 x6 L( `3 H* m k0 S- Y8 j% G0 o) twww2.tvboxnow.com * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
. R: W. e& U8 u* J& p7 z5 z$ Ewww2.tvboxnow.com * A shockwave from the eruption could have blown a hole in the cloud deck.
$ a1 a8 @) W7 I$ W& r' _5 d公仔箱論壇 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.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。: v7 E+ e6 G) i
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7 r7 ~& m* ?+ q% I1 j- }4 CTVBNOW 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。Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. www2.tvboxnow.com$ K7 d8 R6 ?! |1 d7 K
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
/ s0 V9 y9 I/ R( i) ^( k 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.
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" W' H9 U4 @! p' u" lTVBNOW 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。Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes intvb now,tvbnow,bttvb5 d# \- b" m. l1 A$ {0 p& p
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 h% H5 v: C) G2 T6 k
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in 4 z3 T/ C. T2 z0 k
this picture are from forest fires ignited by lava.
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3 {0 e5 a, ^' z8 ?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% c8 z( `5 ?# b3 L7 g0 [( ]9 T& ?
also be the oldest-known active volcano.
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8 o, p/ x u6 [' V7 n7 @tvb now,tvbnow,bttvbA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high : g, t; w2 H# t9 g+ l
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.3 F5 o6 L/ L' B! z% {
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. ; L6 h) s& B( u, e& k/ b F: s; ~
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 公仔箱論壇2 D5 X: Q# X2 I8 o1 Z8 N# ?1 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
6 u6 ?0 `5 h) v5 N公仔箱論壇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 公仔箱論壇' h0 n- n; L) l8 A2 P
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.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( {5 h2 b n
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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 www2.tvboxnow.com/ u: {7 X' B6 k" G0 X8 i
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.www2.tvboxnow.com2 f9 Z9 A7 `' ]% p5 e
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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 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。$ v1 u0 |5 I1 `6 [$ g$ m9 P
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
3 T; w. F0 c. G/ F( Kformed 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
3 @- q) Q3 W( [1 N' `! {8 Bstationary 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.
6 I: Y$ u$ o% r0 G, ?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
2 y+ E$ D. |) T5 p9 m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,
5 N4 S" n7 Y' ^* s `8 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。causing avalanches of debris into the crater. |