One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
7 E8 F' ~3 r. v: b2 {$ Ceruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 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 E/ j) n6 _$ W1 M
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
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erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
6 Y& b, M. S6 O! p7 I2 vand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
6 m. Q* L+ n& @$ H" t# j5.39.217.77:8898They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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- L; l, R3 C2 K# p. I9 d8 KMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 5.39.217.77:8898+ j9 V$ Y, ?7 e% z# R; l
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas公仔箱論壇$ w/ c5 u& y5 K. @1 l6 C) I
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
- A# h; s- \" \9 Y; C5.39.217.77:8898plume 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
5 j! v& ]" Z3 E( tsatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
- D% ], u/ \" H; C: \years. The island’s jagged edges were created by massive avalanches.
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( e' I5 X* d. s. ? YTVBNOW 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。Augustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring $ f* I( w! _& L0 F: {6 Q
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
0 V" m6 z' ^( s: Ztvb now,tvbnow,bttvbocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
9 F) k$ V8 p6 f6 G1 [公仔箱論壇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
/ G: r, |9 O- B- d4 t! v5.39.217.77:8898in 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 L: s. K# W5 A1 X: k6 q) J4 Y) O
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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 5.39.217.77:8898! }6 P9 ]" m6 K! ~: u, c) o7 P% V
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
" W* R. g$ t7 f W5 J) ]2 W, was a pyroclastic flow.tvb now,tvbnow,bttvb, n7 @9 m l) E/ i. W/ x8 o0 V
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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) L" y- O9 Y+ j! p1 s% V
6 E0 A4 Q* N* E/ z b' O. x, h; s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.
' T3 t0 o) k9 z7 t9 {公仔箱論壇 * A shockwave from the eruption could have blown a hole in the cloud deck.
0 [$ M% ^ x6 [) f' qTVBNOW 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。 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.4 [; ?5 \$ @7 ]9 {$ S" e
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. 公仔箱論壇) T* R; ]: s: D
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
3 T4 y8 F" I4 o8 L$ e. y3 m the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.tvb now,tvbnow,bttvb* c1 |' _/ P0 @, z% I( z* U
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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 in5.39.217.77:8898# B& c) U% }% s3 f w7 z. 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
2 L8 Q% }" y% w Acaptured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
( _5 s c; R- Lthis picture are from forest fires ignited by lava.
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$ q7 Y& v+ K% L! r6 bEtna 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,bttvb* \) N$ o% |$ Y: S5 _; a/ E, R
also be the oldest-known active volcano.tvb now,tvbnow,bttvb* x1 k! I7 L- c/ N( G
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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 tvb now,tvbnow,bttvb6 z) J5 a& ?6 ^% `& o+ e. o0 p" ?
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.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。% x+ `+ D1 F' B1 Q( q6 P* \
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3 ~& g) m c3 ~6 e8 c公仔箱論壇Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
& \9 D0 c, T Ltvb 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 . w' r; y. ^+ W/ \) p
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 I/ r# c, f/ w) ?. C
of frequent activity. The plume reached heights of around 30,000 feet.4 x: T' P- ]% ^+ Z
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# D$ e* z, c+ d1 b- xtvb now,tvbnow,bttvbThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
0 T$ V: z, b$ J4 K5 w& k W: 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。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 tvb now,tvbnow,bttvb& s! X& [6 Z8 [( s9 W
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.! b/ I! p6 ]" Z- b; I6 p. \
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+ c9 \5 p% U- f+ ^9 f! d0 \9 e: J公仔箱論壇This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
# @9 ]8 l4 H$ H2 A; G( n5.39.217.77:8898is 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 $ m7 O& ^$ S! n2 o% c/ E9 a
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 * v. L @% y% e
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.5.39.217.77:88981 I) l( n" J" q
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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.
( C. X% Q9 [) s& E公仔箱論壇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 N- `& G5 t. u( ]- s8 f
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, . _7 ]6 K6 ^" U
causing avalanches of debris into the crater. |