One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 5.39.217.77:88984 o) C# \$ f# V* h$ j
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
( j! G* x: V& f8 b8 ~0 q5 Wactive each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
8 m, y6 y. N' P8 h- P0 N; O2 w6 mtvb now,tvbnow,bttvbSome volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
$ W. g* P! D) c! e5.39.217.77:8898erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous # D0 W. |) ]- O
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 5.39.217.77:8898% H) L+ n2 o0 K6 E% v; J" \' r1 b
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.tvb now,tvbnow,bttvb# x/ h! Z- t, F+ I
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1 N3 c, Q1 }+ n7 }3 d. kMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above ; D# O' r3 {# ]7 v; {$ x4 w$ r
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas' Q/ Z% P0 F, Y2 i! h( K) n
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
7 b( a" `' K/ K- G* Btvb now,tvbnow,bttvbplume reached as high as 50,000 feet.tvb now,tvbnow,bttvb# D8 h) v$ v' i1 P$ [: m( A
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7 c4 c: d& E( s" q# R, _- s5 ]# v0 F* c% H5.39.217.77:8898Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
+ \ p+ l$ W1 Ssatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 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。* f+ p. ? c# Q) S$ m
years. 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 - n. \+ O9 _2 N3 z5 j
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet tvb now,tvbnow,bttvb' B9 g3 w" h$ v2 R" ]9 Q7 V0 U' {
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of 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* n; ?- W" O8 X1 o O- K! H
the 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 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。+ j% L8 M. {& C* \$ Z, x
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.1 j, V! q( u& ~% e7 c {5 Y; d$ N
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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
) e& M: q+ B! |" R; r! O. r+ 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。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 tvb now,tvbnow,bttvb1 L, A* W% B0 k+ \ W) r( T3 v
as a pyroclastic flow.
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* R7 z' ?. R5 `4 Z& L) b( j/ s5.39.217.77:8898This 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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* It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
" W/ ] p( g( L$ K * A shockwave from the eruption could have blown a hole in the cloud deck.tvb now,tvbnow,bttvb& @( e; |2 @$ ^9 g
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.公仔箱論壇. \/ T6 }+ L) L Y# ]2 M: l4 _0 k
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5 Y$ W& u7 v! r% T& a1 O6 K6 f4 S1 yAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
2 |: I8 [3 n: B1 U4 z& w& ~$ p* _It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 whenTVBNOW 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。 t- P$ r2 q5 R0 _, A. {
the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.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。( r4 z4 i! N0 T" n
, g" \8 N7 c2 Utvb now,tvbnow,bttvbRedoubt 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
/ X( P; b7 o- z$ Z! M; `/ l, g the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
. [, v; m4 ]7 T- @& m; q% [; 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。captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
3 o, E) k( @- }+ o6 J1 O5.39.217.77:8898this 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 may
" ^' K5 ]1 F% M( C9 ialso be the oldest-known active volcano.
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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
! K' j/ [. e# l' q. 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。and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.公仔箱論壇* |( ]( j2 w I3 r9 E' Y
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/ u8 Q1 H' j1 Z$ j! \) S) |" s5.39.217.77:8898Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
K4 p7 U/ J1 J: p5.39.217.77:8898The 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
- e; G0 S. z) Z4 Z+ D$ ^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。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
) u3 J, A- s/ J1 _" 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。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 ) s9 e0 J) D8 o; X8 i
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.5.39.217.77:88981 v: y( ~1 k' @6 V; H
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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
3 r( O0 ?) Z6 w0 Y( _5 ]! E5.39.217.77:8898flows 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 5.39.217.77:88989 c3 x+ Y( k! x9 N v- }+ M; V2 T
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 公仔箱論壇* d0 @ o" o7 q' r6 N# H/ J
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 5.39.217.77:88989 o2 e; B1 b* a: O: o, i
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
! C5 ^4 V! K/ V1 jtvb now,tvbnow,bttvb \5 k# o. F6 z0 I& `' @3 {
tvb now,tvbnow,bttvb) t5 ?9 _8 |* Y2 z5 @; ^% _6 ?
. \8 ?" R7 o7 \' I* F1 b! [( p4 |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。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. 0 L6 A8 L3 o6 M, `5 t
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
3 f2 f3 U9 d' U; V2 q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, 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。! Q: d: w/ e& _# k* R, f! W
causing avalanches of debris into the crater. |