One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
7 `2 w5 S; Z) a公仔箱論壇eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
# c, r5 U% S( ^! d6 y; 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。active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.tvb now,tvbnow,bttvb5 }% u& s# H' K4 _( r
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 2 Q7 H/ \4 c6 ]' Z
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
! }7 w( U2 b/ G# Aand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
5 l& L- u7 h2 q" U; E5 |They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.www1.tvboxnow.com3 K5 V) ?" j1 _5 N
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7 P' f M- ]% `www1.tvboxnow.comMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
2 C! p! w% T' p/ D, R* B公仔箱論壇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。+ ]4 A) A* a2 S4 E) z% M
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash tvb now,tvbnow,bttvb% h- w% s3 n$ w
plume 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 www1.tvboxnow.com; w! w' u5 s0 g3 [1 @
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
) p2 K! w: ~2 u 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。years. The island’s jagged edges were created by massive avalanches.tvb now,tvbnow,bttvb$ b) \+ O0 `7 z! d) i2 \2 ^
" }, L+ U4 K1 M' i2 g* B" jAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring www1.tvboxnow.com Z9 f& T5 f8 Z7 ^( n6 j7 V [
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet & u* x+ k/ N: s
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
/ s& h9 M! u( R1 K1 Z$ H2 v& Jwww1.tvboxnow.comthe continental crust, creating magma that drives the volcanic eruptions
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano tvb now,tvbnow,bttvb, y( @; {1 W8 F/ s( f# i
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.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。% c* k2 @' h6 a( e
- S5 {- L2 A G. E% P. w公仔箱論壇The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
; l' b4 c& d* d* {$ }! i y' z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
, J1 F8 b* L& J# ?( j* P. X1 {tvb now,tvbnow,bttvbas a pyroclastic flow.公仔箱論壇' e8 M# a: u* q3 |0 f5 _2 B N
" s% r7 b6 J+ `; h- _, e- lThis photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:# \( A) f1 ?4 b! I+ ~
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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.
) _/ k2 `0 k1 H$ V0 }" A3 h R * A shockwave from the eruption could have blown a hole in the cloud deck.tvb now,tvbnow,bttvb* q5 F$ f( E- C/ v/ s! v* E
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.( d0 p M% n$ [
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
R. ~4 _' @# j3 Gtvb now,tvbnow,bttvbIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
! v& D6 M. y3 `/ f8 M7 i% 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。 the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow. h+ ?: ~* I8 @: m" j& s
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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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& q0 _8 y: g) q3 F$ q$ @www1.tvboxnow.comMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
; K0 w- n3 H: Q& n* t 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。 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. n9 N* S* `1 \. {8 K5 n" ocaptured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
- m/ ?0 Y" z* ^4 R w公仔箱論壇this picture are from forest fires ignited by lava.& G2 s' S2 O7 q& \" `
$ R: G; M! S0 S) bEtna 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
, I i6 K$ [' u! 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。also be the oldest-known active volcano.
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3 y% Z. R" s9 | t& L0 b' r! eA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
) K& `9 Z/ f8 _1 j |公仔箱論壇and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.tvb now,tvbnow,bttvb3 [* P$ c: z6 }" I# G7 P1 q
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公仔箱論壇) S# J( Y8 \' r+ R3 k5 t# n' j
; y4 I1 k- W+ 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。Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
6 G) k3 z3 F8 r6 ytvb now,tvbnow,bttvbThe 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
) M$ ]# n; V- u1 s& vmultiple 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 ' ~+ ~, n% O" l# p" n2 I: k6 J. F
of 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。' P8 h" d6 a1 e g' |
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
* ?! z) p/ D) Q4 {3 T3 G, ~west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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6 W1 Z: S# P1 Q$ F! N. gChaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
& O, T. O5 R' r% f0 Z: ^. w @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.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 j! S9 C$ L
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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
) A0 K" V2 Z- \" q7 `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
" b7 L" ?. C! C$ b1 e& 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。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
8 s K8 _# U9 l6 j" Q5 Cstationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.tvb now,tvbnow,bttvb* h1 k- C% G" e" v2 g2 d4 J
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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. tvb now,tvbnow,bttvb( z# f+ \3 ^( j" d
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
9 K2 I- O9 P! ~8 |! Nwww1.tvboxnow.comthat 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,
# B! U, F6 _" C6 A; E; r# jwww1.tvboxnow.comcausing avalanches of debris into the crater. |