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。9 B0 `+ w4 B- \' A7 l' N
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
1 T3 K7 n1 b! C3 w5 |1 I% t: _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。active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.tvb now,tvbnow,bttvb$ i0 `! v- K: W6 X S( ]/ t5 d% w! j3 @
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 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 Y! D$ M1 q% [( Y0 A
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 5.39.217.77:88985 k I6 T" J' ?
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
) m' L: U4 j% EThey tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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: |" G: x* R) V7 f8 }' G$ u公仔箱論壇Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 0 C" C/ w; e) O$ T/ R" K4 E9 b
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewasTVBNOW 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。 o" J4 L4 F1 M) X, E+ L& }, o& _, i
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
! v& ?" X$ q* e; \( H6 \- J* Cplume reached as high as 50,000 feet.
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
T. ^, C+ w1 U/ htvb now,tvbnow,bttvbsatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
3 i/ F3 H9 w; u* t- ^) yTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。years. The island’s jagged edges were created by massive avalanches.5.39.217.77:8898. ~1 z5 `1 ^+ P) m7 M# m
9 a- E4 I5 n- c, f+ B& k5.39.217.77:8898Augustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
. z' q% K( H6 q3 j' |of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
/ ?5 i5 U8 O: H' M( I5.39.217.77:8898ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
2 H0 w, M3 v+ |3 q% othe continental crust, creating magma that drives the volcanic eruptions公仔箱論壇9 _, a4 o1 O* b. ], b2 R u
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- I+ ?/ k0 y" r. ftvb now,tvbnow,bttvbAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。5 M( }4 y* L$ m/ b6 C. l
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.tvb now,tvbnow,bttvb+ g& B( V8 K) r/ ?: \) U
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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
8 g: }# F" _- Z' y: yand 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
' }9 N8 g: S0 P( ?tvb now,tvbnow,bttvbas a pyroclastic flow.
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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:tvb now,tvbnow,bttvb. O- K) K+ h! c# x+ l Y
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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.
+ a3 G' X8 X- G2 B M) F0 c" k% i公仔箱論壇 * A shockwave from the eruption could have blown a hole in the cloud deck.
+ }/ L" P, @! f6 XTVBNOW 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。 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.$ C- _/ d) F" m- X; {) H& ?2 P
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) h k# |# e1 L; A7 e, L3 g8 N/ ^# {公仔箱論壇Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
) f: P6 R x' r, q; I& m5 F公仔箱論壇It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 whentvb now,tvbnow,bttvb1 m5 B! ?& G& a+ P6 s" Q/ ^
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.tvb now,tvbnow,bttvb5 S, ]- t u- Y% v# V! r$ R4 G: R
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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。5 F4 K0 ?; e* ~" v9 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
0 t9 B- X* n' D5.39.217.77:8898captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in 8 q2 j) o3 q7 W6 L
this picture are from forest fires ignited by lava.
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3 c: ^6 s a, j- ZEtna 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
) |5 W) R: ~5 ~; S7 k; ralso be the oldest-known active volcano.5.39.217.77:8898/ A+ M% r4 ^4 I, I* R6 q2 E! V; w
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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
2 G$ Y3 x9 T/ u; N3 ~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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+ |! {4 c1 T2 l2 a8 A2 ZPopoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 5.39.217.77:8898* M$ A4 q) y" @' 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 7 D- l7 @+ D3 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
& F: |- ^- C. f. i2 U& n+ Uof frequent activity. The plume reached heights of around 30,000 feet.公仔箱論壇$ `- v) i# s. U. n; V0 ]
! o/ g9 H/ C* v9 j4 u ?4 \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。
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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 i* y. @# E' F: a) Y+ j: M' Z) Q
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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7 y7 e( b2 ]/ o' r* ^+ b3 j7 O0 n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 5.39.217.77:8898) x b1 c% p5 Z% ~% P z* Q4 j5 [+ k
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.- r# N' T% r/ v& M+ e/ w/ t- Y
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5 e9 F; a0 x: t( y. U5.39.217.77:8898This 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。 S: Y: e; a2 d, n
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
+ p: ?1 [/ ]4 L0 L4 L5.39.217.77:8898formed 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 5.39.217.77:8898* H* O$ ~: i; y( v
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. 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。$ P9 J3 r4 I: E6 [6 p
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
/ |& }. M, V) R6 n W4 a1 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。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, , v& m* e9 H# c# ^
causing avalanches of debris into the crater. |