One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 公仔箱論壇4 N: @4 g ?# G( e8 L* ~' M- L
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 5.39.217.77:8898 x" a1 Z5 X" E) r) u3 W( V
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.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 v, q. Z( O1 a
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
1 u+ s: J t$ x; e5 [, `erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
7 e7 |, R E) l1 s9 X; o! z' b公仔箱論壇and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
* N5 A3 n9 o9 u, n; hTVBNOW 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。They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.5.39.217.77:88987 D' K6 m3 N" Y1 l; P: H4 P* |- n
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
, Y6 N# u3 \" `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。of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
6 N& n9 \7 d+ x% O. ?) v; }6 N( qtaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash tvb now,tvbnow,bttvb2 t8 E8 c+ L0 @/ A
plume reached as high as 50,000 feet.' W' `# _8 ]# G1 W! Z; d& ] U
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" {2 t" ?& y0 s8 H4 R% ]+ @公仔箱論壇Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
8 U$ v0 P2 ]7 m" [, p2 W$ jtvb now,tvbnow,bttvbsatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 公仔箱論壇6 l- v+ G( c: s1 @( Y! V X, ~
years. The island’s jagged edges were created by massive avalanches.2 a' [/ |% q% A; S
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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
1 v- c( i) ]* m6 {/ P! zTVBNOW 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 Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet 5.39.217.77:8898* T- m4 ?% O4 I* W
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
" ^/ r! ]1 l5 F3 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。the continental crust, creating magma that drives the volcanic eruptions( [9 s9 S. k+ t$ B0 b) S0 e/ j# e
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# w3 A2 _5 g9 a8 A% @0 j# ]Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
% j+ [- o% Q3 L+ F9 b/ q5 A2 p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.公仔箱論壇! E- }3 }: O4 A. R
* y( v7 U6 D7 x6 G/ f5 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 smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising tvb now,tvbnow,bttvb2 u3 _6 E+ n% U
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 * K* ?% I: Y( E. S" T. K" K% ?
as a pyroclastic flow.
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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:5.39.217.77:8898, v T+ V' F8 N; K0 c/ ?
/ e& N4 `( m* n* q- w公仔箱論壇 * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
. g) A" d* q' ]) @; f( X. h5.39.217.77:8898 * A shockwave from the eruption could have blown a hole in the cloud deck.
/ ^/ p( v$ s3 w' L4 w5 }# ^5.39.217.77:8898 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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; @" b1 b, s# MTVBNOW 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。Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. 5.39.217.77:88982 [! S% F* d. R' [
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
n1 q% m- p9 HTVBNOW 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.5.39.217.77:88987 |. D% L7 t E1 ~$ N
6 S m( x& D1 l F; U4 u# H& Y公仔箱論壇Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.5.39.217.77:8898+ |3 a& @" `' E2 R& h
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0 _/ B+ A* n' \$ F6 U5.39.217.77:8898Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes intvb now,tvbnow,bttvb* X& Z* g& M9 i9 X- h" I3 c1 R
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one tvb now,tvbnow,bttvb# m* u1 h) |, [& L% H
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
' L) K) \' i B公仔箱論壇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 may
5 A7 n q( L+ M* Ctvb now,tvbnow,bttvbalso 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
1 ?) H0 W* I8 D/ u5 N# F# o2 x0 W |tvb now,tvbnow,bttvband 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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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 h8 _0 |! y( ?: g7 x$ a- R
& N5 p( U" F( W2 hPopoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 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。! H5 L' Y7 q$ E( 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 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。1 }- t( V" o+ @" f! G' c3 y
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
1 h' W5 G/ v% W/ d$ btvb now,tvbnow,bttvbof frequent activity. The plume reached heights of around 30,000 feet.
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W$ E- C$ M' Q) _This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 公仔箱論壇2 h+ t/ d" n" G' _5 u" 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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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 ~6 j7 {/ A* S7 m2 ]
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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" w4 {2 M1 T# `2 d+ q- S. R. h; 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。, E" L1 o- ~% E6 |! U! \
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。& E* h; k1 Q4 z1 V9 V) U& y/ P
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
h2 d, V, D+ S; D: b" n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 : Q- u2 c. Z) h1 p; s+ G
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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6 f7 { s, m& V( _" K4 m, ETVBNOW 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。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。" K: W0 Y' `* B* U3 e
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.
2 S1 ]/ n$ S: Q) a5 ktvb now,tvbnow,bttvbA 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。+ T. T/ m( p/ O' V' D9 w
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,
9 r- L1 H5 S, Z: ^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。causing avalanches of debris into the crater. |