One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 公仔箱論壇3 I! p- j8 Q- R* a5 m m
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
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Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 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 A" L: H' e
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
V( p6 x' Q6 U8 v7 ~5.39.217.76and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. , _3 c' y5 e2 l" A
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.tvb now,tvbnow,bttvb" \9 I2 _3 b+ d$ l* z
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 公仔箱論壇* s" V5 ]* O |, w" X3 P! H& c& L
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
9 V+ x B/ `0 @5.39.217.76taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
; G _. P: n5 [+ f' g- S! k0 UTVBNOW 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。plume reached as high as 50,000 feet.
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# E: V5 C% a8 K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
9 i, D1 P: p9 {+ Z" }* G公仔箱論壇satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
; f3 f# |) b/ h. ftvb now,tvbnow,bttvbyears. The island’s jagged edges were created by massive avalanches.
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9 W7 k; W1 p4 L; Jtvb now,tvbnow,bttvbAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
4 x0 Q& K5 s& k3 ~: h- oof Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet & [" g' x7 ^8 v
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
+ v. k5 f3 \( h {7 ?tvb now,tvbnow,bttvbthe continental crust, creating magma that drives the volcanic eruptions
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& V+ ~ O' s9 D; b) ]. s. I8 _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。Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev 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。: I0 U1 O9 O# P( M( A5 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
# E& d. L4 q K* n0 n( Z6 DTVBNOW 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
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: c" R; q% f7 Y4 Y1 ^, r. e5.39.217.76This 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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* It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.5.39.217.76% F! `6 t/ j V& p1 B1 [0 @
* A shockwave from the eruption could have blown a hole in the cloud deck.) H- h, }: }9 k7 m9 @) h
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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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,bttvb6 Q0 q5 V" X7 K0 Z
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 whenTVBNOW 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。# O3 h- _- E8 f' d! F
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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# Q% r& s8 L4 A7 _1 ~; Y; ^Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.5 F; A1 U% {; c) m" g* D( Y# |
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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。' V3 s3 h0 P, r# A3 N; k
7 V) u, a7 r9 u/ p" {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 in
& H+ b3 B+ S" m8 S9 f6 q6 U8 p' z0 ctvb 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。* a4 q+ |5 S; F% P# Q6 ^. x' k5 C- i
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in 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 m2 k4 C/ W5 U# |5 R Z
this picture are from forest fires ignited by lava.5.39.217.76! A. S$ _8 {# N) o% E. y: O
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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
% w, h3 U" z/ x9 ?$ l! ]& L5 f! C1 j2 yalso 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 公仔箱論壇# ]" T6 w T8 Q/ x
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.
4 u: S; T4 H& JTVBNOW 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 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
6 A4 B. w% W9 S- P# I* R8 p+ 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。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
; S8 ]' ~ J2 C/ z公仔箱論壇of frequent activity. The plume reached heights of around 30,000 feet.
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& b* P5 s- ~. }/ }公仔箱論壇This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the . h8 Q3 M. Z9 k, J- q$ T
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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" m+ I5 J: |( B4 ^+ B$ Q/ e5.39.217.76Chaitén 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,bttvb2 D' U5 |, E5 k. Y- B
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.1 T9 i* k0 q$ b9 l1 I( s2 |
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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
) e) |0 A' ^ |1 I# F* 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。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 公仔箱論壇. b* s9 n5 N2 G2 h: o5 b& X
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 公仔箱論壇) M' z: d5 O# f' k
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.
7 j( U" u7 Z* EA 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 ! t, Q* ~7 L) X& t
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,
, V" [, y1 C% {, W x Gcausing avalanches of debris into the crater. |