One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
; l) X& l7 |! }2 }# Gtvb now,tvbnow,bttvberuptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 公仔箱論壇' F5 _7 s6 O* U, C N9 U
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。0 ]. g. J5 o% X4 \, |7 b
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 公仔箱論壇. W% o, h* t( S3 s
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
: F# C* K3 Y. c5 S: { }8 k$ Vand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
% o, f& A, C0 d. i, Y公仔箱論壇They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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) c7 y, u5 s* R' o+ L; a4 lTVBNOW 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。Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above % k# }# m! w: A* W" r! G
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas8 r- }! y9 A! o" x4 z4 C4 n: Q8 f
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
: z" A: d& r9 }9 ?. _公仔箱論壇plume reached as high as 50,000 feet.
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
6 e' u3 L1 h: i: ~, h: w1 Ktvb 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 5.39.217.772 }/ i8 Z& a+ z9 b- e
years. The island’s jagged edges were created by massive avalanches.
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- x5 D- X3 s4 w5 N3 z4 l' Y0 LAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring 5.39.217.776 ^: i, F4 m+ G
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
+ {% L* V" U- R$ g" U, O8 p5 X5.39.217.77ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of tvb now,tvbnow,bttvb- p, g; L5 Y9 j4 O- M y
the continental crust, creating magma that drives the volcanic eruptions
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1 P) Z o6 R/ }' aAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano 5 \* I5 `: D/ ^: ^5 E3 q% V
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
: w4 j& n1 W" T; 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。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 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。. G5 b6 }3 o8 W
as a pyroclastic flow.
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, V* n, ~3 c( t" J6 m! YThis 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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7 m0 A# F4 k0 \" E2 f8 B * 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' U% |7 @* k5.39.217.77 * A shockwave from the eruption could have blown a hole in the cloud deck.
: b" l7 l. l/ i) ?3 h& G& X! g * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.tvb now,tvbnow,bttvb( m5 @0 k! Y; T: f- ]
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, Q. p& S+ j; K3 z" Ltvb now,tvbnow,bttvbAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
- I( A0 k, G8 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。It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when% z* s- h1 K/ }2 a \
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.3 P8 V2 w& O8 N7 f* ?
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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
& w( I, h/ N! N; \$ Otvb now,tvbnow,bttvb the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 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。9 N- }0 { w6 P* @
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
+ N7 s7 E* k; ~0 x; c c公仔箱論壇this picture are from forest fires ignited by lava.5.39.217.77( }" }+ B. ?! `6 S9 r
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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公仔箱論壇! T; O Y2 {4 U9 @
also be the oldest-known active 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。. ~7 u+ W2 c0 b2 o
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% f! B9 O, Q5 D' aA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
! Z' u' j& U8 g0 |& N' X8 h5.39.217.77and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.# _; V2 E, S! Z; Y6 s6 N
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: ?' J. e5 ~7 XPopoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
* U W0 s4 I' t# \0 _- u, C* [7 z公仔箱論壇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
/ h4 I K* l) ]8 u# o" ]* ]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
+ a4 c1 [5 B$ g, e% L3 i8 ]. S$ mof frequent activity. The plume reached heights of around 30,000 feet.
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/ [! q( V* D0 R( O: ]: i! oThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 4 L$ u8 l; f6 K9 `) r* s. k
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 5.39.217.77+ ^5 S2 L' } q. ?# 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
5 x7 c' O* i# @/ S2 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。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
|+ f0 u/ o- K5 ATVBNOW 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。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
; }) J" K2 F+ V# h4 n; Xstationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.公仔箱論壇6 L$ w. N3 u u+ Q" C8 y# V: E9 N
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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. 公仔箱論壇% q. ^$ c+ g* M4 o" U. G" u
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
8 Q+ \8 l: }8 }% P) q" G1 `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,
/ l& V5 h M$ M3 l0 N0 ^5.39.217.77causing avalanches of debris into the crater. |