One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 5.39.217.77( U/ q. x" {) Q+ m+ o7 e( n, [) T
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
5 x8 e1 ]. @3 F6 v3 g公仔箱論壇active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.5.39.217.775 E7 D* {& A, n! l! f' G7 ~
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
5 o9 u: M, v- I5 c- o3 A! Q" U$ \公仔箱論壇erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
V( V/ `& l' R% i0 z4 XTVBNOW 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 explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. tvb now,tvbnow,bttvb" y9 o5 A" O, Z; { Q
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
5 A9 L4 G0 V, Z ?' N" qtvb now,tvbnow,bttvbof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas5.39.217.77 h" j3 X9 k$ P+ ~6 o
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
2 q& f- l6 o# y5 B! H9 r公仔箱論壇plume reached as high as 50,000 feet.5.39.217.77& ]" W; c" {- s1 |( \# K6 Y0 C
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 5.39.217.770 G8 {2 L& `: U* n" ~; q
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
, B; I7 J* I8 l1 @) Q2 H( \$ V9 k公仔箱論壇years. The island’s jagged edges were created by massive avalanches.
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& M2 v1 ~" [# s! ltvb 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 ) y6 I: n4 A: y0 s9 @" k" N
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet ; _, {' D# m- ~5 ^3 ]; x
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of 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。5 I3 U$ O& _% g. f; v
the continental crust, creating magma that drives the volcanic eruptionsTVBNOW 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 V q; ?: K% s3 T: a, ~
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& B# K1 m0 ~3 `# gtvb now,tvbnow,bttvbAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
. d- h, L5 V$ E! n. O: T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.5.39.217.773 B; v1 I& E2 B2 Q
7 t% e+ G: m1 YThe smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising ! Z7 T- X: B! x) } u" I
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
0 g6 ]/ j- u7 k; L0 ]" k公仔箱論壇as a pyroclastic flow.5.39.217.77( D! {' l+ l3 Q" k/ y; A
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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:5.39.217.778 a! X2 W3 V2 A6 F$ w
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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.公仔箱論壇% i0 |2 i7 a8 d, }4 B. N5 F o% R
* A shockwave from the eruption could have blown a hole in the cloud deck.tvb now,tvbnow,bttvb1 ~$ {8 g- g$ e; P7 ]. P
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.5.39.217.77 g8 [8 o( a, K0 Y; j- G
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, {# L1 ^& Q" s- b. j8 ]tvb now,tvbnow,bttvbAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
9 ?! s- Y% E1 A0 p9 _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。It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
, k2 u P+ N' t* V) I the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.5 w' |; E4 N! D% ^- F4 ?
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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.公仔箱論壇9 p' W5 ?" m4 b) T9 ?6 T
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4 G7 C0 i+ {* _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 intvb now,tvbnow,bttvb' d& o' A! z, S5 X/ V4 V7 `" z
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 0 Q: }% t0 X8 x; U" k9 d
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
5 L& H) T* j, \! ^+ Qthis 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
, o% j% s, B5 E1 d公仔箱論壇also be the oldest-known active volcano.
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$ H# X$ H5 F6 X* {- ]. ]A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
1 F+ p8 C6 G: F: 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。and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.公仔箱論壇& A e- X$ L# q' U
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
0 x: S2 Y5 Z! I7 E- v8 u. }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。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
1 q7 t: p7 _; v$ G; b5.39.217.77multiple 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
4 |, w9 ?6 x0 S* F8 G! Y5.39.217.77of frequent activity. The plume reached heights of around 30,000 feet.tvb now,tvbnow,bttvb+ \! ]% w) |$ i8 t7 l' x$ k+ [
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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。7 x2 z/ X# u* z$ Y: m* q
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
4 G/ F J+ z! M5 s, J+ Ktvb now,tvbnow,bttvbflows 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.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。* m- ~$ U/ x' M' S7 O; `4 w
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/ K6 z3 M* h; E6 \9 aThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
+ R* u5 E; Z$ ?6 r) Y# [* P; Ztvb now,tvbnow,bttvbis 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 5.39.217.77' p6 X/ `9 ^1 G
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 ) m2 r' P2 f$ Q% J! n, U
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.
/ _, ^( x8 T1 DA 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 5.39.217.77/ n7 V; [0 `8 `! O: M
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,
# e% E, f1 Q$ j! j, ~causing avalanches of debris into the crater. |