One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic $ C! Z2 g1 r& z; J+ F
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are . X( I1 C6 V9 C
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth." u0 {, C# t3 K6 K, t
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, www2.tvboxnow.com# D: ~" d& g2 f
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
7 A% \+ R" R! ^! Y8 w2 iand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. ) \9 b: W- X" {% h; Y& {6 @+ {
They 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 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。$ l6 _7 J; b2 T* b' p. W* B1 ]# ~
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
' S0 U4 E0 m+ g/ j7 btaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
, G; G" d9 g- }+ {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
K2 ~' Q y3 k公仔箱論壇satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 # Z( j: a2 r/ _7 m m: D
years. The island’s jagged edges were created by massive avalanches.
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- t- z, m: Y3 z+ _Augustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
0 x5 Y8 @# t4 |* @" X2 lwww2.tvboxnow.comof Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet 4 l: q& w+ d% V( ?. k% }0 L/ y
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
2 M4 n- X5 R* X/ ~tvb now,tvbnow,bttvbthe continental crust, creating magma that drives the volcanic eruptions: D' P; t: { J* S- z9 Q+ Z# Y( m8 v* J
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. J( M! z5 a5 a3 n" oAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
?: X9 ?+ @" K1 o! n% F公仔箱論壇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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. g' D1 f) k# D: wThe smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
H9 y1 i* }% i8 j0 |7 {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。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
/ q0 p' j! X" k& U+ ?www2.tvboxnow.comas a pyroclastic flow.4 a# V) P7 m4 @- Y% g2 I3 l
& S' x# ]* N. E/ h Y! R6 BThis photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up: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。6 L6 X6 C1 m# u) Z7 c! c
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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.www2.tvboxnow.com7 z1 z/ _ K; Q, y
* A shockwave from the eruption could have blown a hole in the cloud deck.
' `% u8 q" W) U公仔箱論壇 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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) Y" e. M# r$ L- VAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. www2.tvboxnow.com, d- ^) e, ^( [4 [% Y% Q7 p& b
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
; N' ~7 h- R2 l+ F( U the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.公仔箱論壇# w/ s; J$ j6 O
) r' Z+ Z+ x$ I/ i5 TTVBNOW 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。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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0 o' L0 f `) c" G1 H" a; _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。# O- d# ^" M0 a6 N
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one www2.tvboxnow.com! s0 K( \' [9 y" l |7 z3 i9 j
captured 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7 ?/ I1 e$ v5 Z* P, M
this picture are from forest fires ignited by lava.tvb now,tvbnow,bttvb# D6 j/ M6 a( m, B
% C8 M6 u$ U' w$ E3 {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。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
% z7 b J4 r9 p- calso be the oldest-known active volcano.
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! x1 w) Q- Z1 V a+ f6 L! C公仔箱論壇 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。3 f" Y" ?) [* a6 k' _1 e
( r7 f/ U3 L m( FTVBNOW 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。A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high 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。& n# s ?6 `! s2 F* U
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.( P3 C1 }& v1 p9 X, }; q
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8 W, G# K9 d; M7 ~3 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。Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 公仔箱論壇( G1 ~# h! l5 m1 y7 a+ [4 N
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 t Y1 |$ L& e: Smultiple 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
7 w( o: W! }" a" a" f1 R9 Gof frequent activity. The plume reached heights of around 30,000 feet.tvb now,tvbnow,bttvb" o* K9 l+ ~: W5 d$ f# `9 H& E
" o4 p! q' C/ o6 S" C! s, 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。 www2.tvboxnow.com" ^) ?# B; D# C1 Q6 y
9 O4 S! S' o* `, Z }www2.tvboxnow.com tvb now,tvbnow,bttvb! x) K+ a* d) E. U. V
0 A3 i3 @8 i9 M5 u3 M4 w' l' U5 DTVBNOW 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。This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
% v/ n- c$ |; [" G/ R8 r" [www2.tvboxnow.comwest coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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! j1 H0 Q% r* CChaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic tvb now,tvbnow,bttvb9 _8 s; h* V/ m" H
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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% t3 v9 A. c0 y2 E1 e, Z" cThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra 公仔箱論壇5 l0 }: U4 B+ b' E6 R$ `5 {
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 tvb now,tvbnow,bttvb V% |+ `' G4 p( W
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
- q6 P* u9 F. m& Jstationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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0 x1 E) _7 w7 U" L2 X; Q( [( WNASA’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. z5 N+ Y6 X: t# u9 H) o
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
7 |/ u) t4 O8 Y5 I' FTVBNOW 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,
& b' b _+ h) i+ u" X6 }# @0 bcausing avalanches of debris into the crater. |