One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
+ D5 T1 x/ e% d% P) Z' g, seruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 公仔箱論壇$ L& W T( S( z
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
4 W) A3 N" D; r0 y# vSome volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, tvb now,tvbnow,bttvb7 [3 a; W' p2 C( M- D2 v4 ?5 u
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 公仔箱論壇. o/ C8 P, v+ ^ Y
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
+ d6 Q }( y, _( z( ]2 [公仔箱論壇They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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0 A: p7 y8 ^8 g, M. rMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 5.39.217.770 Y6 }& s$ ^, e. p
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas公仔箱論壇6 B- U r& D& a: D, P
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash 7 [$ o6 ~; L* E9 q8 }
plume reached as high as 50,000 feet.公仔箱論壇 o9 ?9 T8 t2 W2 R) f! I
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
$ P! b% ~/ E+ m) I# ]2 ^4 G$ Xsatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 $ w( ^, N# B9 T' Y; i7 \, p
years. The island’s jagged edges were created by massive avalanches.tvb now,tvbnow,bttvb: k$ d$ }# j+ }& q4 g7 i6 [1 S- C/ ?
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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
& ^ O; d, E/ s+ N! s9 cof Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet 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。% O. Z+ A" |2 b/ @8 @0 D$ ?7 K
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。( ^2 t+ y; |* ?0 a. n8 y' R% A
the continental crust, creating magma that drives the volcanic eruptions
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/ T+ V, v- Y% V' m5 [2 GAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
+ @" j' c7 r' `- J' n+ x; ^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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( n5 A) d i3 R' j7 sThe smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
9 [ t* ~7 ~) P6 Wand 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
) Y4 W f: }) Z" Vas a pyroclastic flow." c! z/ P. o" y) j
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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& h# C$ F% t9 |
6 D8 S. ? J6 I6 [' @tvb now,tvbnow,bttvb * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.公仔箱論壇5 y# A0 }: q$ D& m+ s
* A shockwave from the eruption could have blown a hole in the cloud deck.
^" c9 e0 B8 n0 M * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.公仔箱論壇9 {5 {' {% I8 w
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. tvb now,tvbnow,bttvb Z+ A- {# S5 q; J( a
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
# }* C( t" b; i( l9 i& V- f) m4 ? 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,bttvb& z# |, R3 o1 a* V: r4 E6 \
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1 E0 `* R/ p$ O! k1 u5 |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。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。! p. v* o* _6 }5 [; w/ 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 5.39.217.77( X+ ~3 C# v; h: r5 X$ `2 r
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in tvb now,tvbnow,bttvb) F4 [( m& _# T0 _
this picture are from forest fires ignited by lava.
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& Y X! Y5 L$ M; J8 \ V公仔箱論壇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 maytvb now,tvbnow,bttvb7 W7 e; |. A- m" L: y* v5 j6 K
also be the oldest-known active volcano.
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" m2 W9 r0 ]8 K" vA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high 7 _0 z6 n3 D1 k$ v0 F& s2 Q9 a9 I4 ^0 F
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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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 5.39.217.776 \5 q: Z; y, J% ^4 c& K
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 tvb now,tvbnow,bttvb2 r/ L! N' T9 b
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
5 @5 M9 {; q1 m( l" b" T% z- ]公仔箱論壇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 : g0 l. G' t$ _* x$ s
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.tvb now,tvbnow,bttvb& r0 w# q. W* Z! D! _
4 N' u" L6 e( @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 / Q9 {* J( P7 s% J/ R" X
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.. `! D- x& O; @/ K7 K9 ?9 x
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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 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( Y7 j. o7 A$ H
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
- Y8 `: t5 Z8 u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 tvb now,tvbnow,bttvb0 w( t* f% O% j9 m; [2 H4 C% \8 i
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.tvb now,tvbnow,bttvb% S) O, X) a- V& o7 q
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1 R& K* Y# D6 _( L( y公仔箱論壇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.
e" X t2 g! N0 B( o5.39.217.77A 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 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( U: h- b# k( s f6 Q
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,
* G0 T; a. Y' ~) N$ p# T2 ncausing avalanches of debris into the crater. |