One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 5.39.217.77:88988 n, R9 o. S/ {1 L6 |8 b2 x5 h
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
$ |3 f5 f' }, P7 u7 s+ J [active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.公仔箱論壇- m+ i1 t/ s& O' _+ m
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
) S( |) ~; F) d2 G6 J% T公仔箱論壇erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
0 G4 c( Q) u" ?1 l. ^! [/ X4 Yand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
( o. `0 n- {& J* {) t1 aThey tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.公仔箱論壇3 i+ _0 r4 n0 N b- ~- F) T8 [- z
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
9 c7 B# _7 y! `; C公仔箱論壇of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas5.39.217.77:8898; a4 X7 V1 _2 B' g
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash 5.39.217.77:8898- i4 J' T. i3 n" Z
plume reached as high as 50,000 feet.
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8 d! `' Z# T1 z8 j1 qtvb now,tvbnow,bttvbAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
# k. P" k) K2 Y1 t% OTVBNOW 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。satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 5.39.217.77:88984 v/ R! i% e1 ^* j& E C; H! C r
years. The island’s jagged edges were created by massive avalanches.
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) J2 P6 H/ N' `: V7 T8 NAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring tvb now,tvbnow,bttvb" K" x' I& y, I& f8 z+ X0 z$ u
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
8 W$ y$ o/ c ?! Z% _& iTVBNOW 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。ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
8 U) j( n# |$ h Mtvb now,tvbnow,bttvbthe 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
5 ?# g, J9 Z# U4 P" Sin 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4 q8 f7 i5 y8 ^: o( x
2 c. P" Z1 n+ ?% E; 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 smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
7 d! h0 w# \( ~9 r( Rtvb now,tvbnow,bttvband 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 ) a" S4 y8 o* b* D/ c' J
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:
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3 d0 } x! ^! p* H# y* i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.
& p. z- [! w, q4 O/ \4 xtvb now,tvbnow,bttvb * A shockwave from the eruption could have blown a hole in the cloud deck.! r( Y% ?& g8 N$ ^
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.8 {. v- I: R6 u' I
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
. `# I. M0 {5 k/ l公仔箱論壇It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
5 W8 r9 x G: n0 G the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.$ S9 [9 h5 v- ^5 g1 N3 w
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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.
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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公仔箱論壇- f) g8 W! b4 f: K2 I6 b
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 5.39.217.77:88987 ?- R. j, d! m) S* u
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in 4 S. n( n1 Y/ _2 |0 E
this picture are from forest fires ignited by lava.5.39.217.77:8898( e! v. C) |5 h# e
9 C$ V* W( a$ m4 HEtna 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
. u, M3 E2 s' f# [" v0 utvb now,tvbnow,bttvbalso be the oldest-known active volcano.
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$ @4 h/ w$ F: G, U, k- s# m' ^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。6 a& y( O8 \5 b& Q/ B# ~4 v
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.
: Q2 X6 c- C" Y* ]6 X3 S8 Z: ptvb now,tvbnow,bttvbThe 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* G5 `" V% O& q
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 ]" ^+ E- @7 v0 V7 z) ?& x4 k# lof frequent activity. The plume reached heights of around 30,000 feet.
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" ~+ C* Q2 O' f+ R% s$ u, |This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 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。+ r l( C, @6 y% ]8 E! k
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.' v( f: c! y0 F) 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 公仔箱論壇) n/ c/ \4 y% 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.
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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 # b/ m" M$ q! U6 j( W3 e5 r" F
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 + ^0 p$ s% Q' G5 P- p7 t& q" Z% J% z
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
$ u% o5 U9 E" c- A公仔箱論壇stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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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.
' X( x$ f/ U9 g2 q9 {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
) V0 l/ |* b: j1 u" M3 ~! ^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, ; P9 q5 x) N4 f }3 c
causing avalanches of debris into the crater. |