One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic " d' i+ C' }, A# o9 y( b3 z1 \5 \
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
3 r: v' o/ b& M* v7 F5 w% w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.tvb now,tvbnow,bttvb! `3 w5 F+ q. ^/ X( ?% e( P
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
% R) f# r, V3 Y$ w, u) }# F公仔箱論壇erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
0 [; ` E# S0 w: [' m公仔箱論壇and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
4 g. }2 m5 E. S [4 U( R5 k0 Utvb now,tvbnow,bttvbThey 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
$ a: h0 t, j( D2 e8 n6 F2 z; ?( bof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
~3 \: |- I7 T5 k. J2 ^, h4 G6 Ptvb now,tvbnow,bttvbtaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
: V$ V& J4 V: _- g$ D: e0 |plume reached as high as 50,000 feet.8 u$ `" R$ H* E6 I; c
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4 U" l: J t" C( vTVBNOW 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。Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
" t/ W3 q3 z* ]5.39.217.76satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
6 v1 ^! @) E; |. s4 c9 s4 A' ]( lyears. The island’s jagged edges were created by massive avalanches.
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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 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。8 g+ T$ i+ i% N# A) t
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
6 s) C: p: C* \3 Gocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of 公仔箱論壇! j' g& T: v' u6 m( }
the continental crust, creating magma that drives the volcanic eruptions
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& r a' [) x% K8 XAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
1 A. J$ k2 z& D3 f0 V; `2 v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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The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
) s8 s- t; ]8 L; n8 Y' _' @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
. H7 B9 h5 L% R: h( M" i/ [, t4 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。as a pyroclastic flow.# u" q$ B }# q9 z1 |6 d
3 X* i; n+ v3 ?& x4 x) Ktvb now,tvbnow,bttvbThis photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:公仔箱論壇# S4 M7 j* x* ?2 z; {
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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.
& |4 N$ ~- ?6 Z, }tvb now,tvbnow,bttvb * A shockwave from the eruption could have blown a hole in the cloud deck.tvb now,tvbnow,bttvb/ c! ?- s. S' X& Q
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.8 Z0 J) Z9 {! Z2 E1 Z
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) b5 C* s+ P, mtvb now,tvbnow,bttvbAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
5 O! _, f: M, \ hIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
6 a/ W5 S6 Z) B+ 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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2 F7 \- V- L, c" u# C& u9 `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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Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
2 n$ j0 P" T4 Q; i( STVBNOW 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
4 ^3 \) _0 j, b( Z, N5.39.217.76captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in , I5 b) X: |6 u7 o, l) s& Z! f' E
this picture are from forest fires ignited by lava.
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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 may8 g/ m y" _ f
also be the oldest-known active volcano.公仔箱論壇$ s1 E- x/ `" @# J
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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
8 }: _+ u1 ]7 B9 b( l" h5.39.217.76and 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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) z) X% o( P' N$ ^$ \4 A5.39.217.76Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
/ e, ^: X w; c6 RThe 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,bttvb- D5 E4 w5 W7 P: I1 B6 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
& a$ M, v# m1 o3 c" U4 ?7 a Y: 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。of frequent activity. The plume reached heights of around 30,000 feet.5.39.217.768 @/ A* I6 n; ~- `) z2 A
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
) q: d' i/ x8 s! G. [: c& k公仔箱論壇west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.公仔箱論壇4 ~( z$ ?2 }. a
: I" I+ @5 A! d' F% R; k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 8 @" o7 }) ^: A( `5 c; d
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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This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
# X M/ V& g/ |3 ~+ m! x% d( {; 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。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 A: j# e4 t) q7 b公仔箱論壇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 5.39.217.764 M: T+ d, F- c i1 H1 J
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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( b7 R+ L8 u" F- ^0 h# ] U6 vNASA’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 H0 d' j q8 {4 @- Y+ g2 y" g [# F8 u* gA 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 公仔箱論壇% C9 {5 ?( b9 p& W; d
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,
# D( Q! [# m" {+ _causing avalanches of debris into the crater. |