One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 6 A- {3 C" \& ?" c, C* [) f
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
& d7 ?; H4 {* y3 h! P( R5 Oactive each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
. F: G$ ]/ U) mtvb now,tvbnow,bttvbSome volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, tvb now,tvbnow,bttvb) }# q% Z: K/ U! Y
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
/ }# p3 X P6 S" N. R- u5.39.217.77:8898and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. h+ K7 o0 \' ?% j7 q# K
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.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。" P$ T! M4 s7 p2 I
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% {; J1 C4 k; ~5 [! pMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 公仔箱論壇; U! F0 P% I$ ~, a7 h* U/ G
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
4 ~8 Q3 e1 u9 U6 L7 f$ S" D5.39.217.77:8898taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash 公仔箱論壇. p" J7 @' Y+ g N
plume reached as high as 50,000 feet.1 ^0 @9 D" a: g( I @# R% T
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra ( \4 @: ^' H! g: X! F
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 5.39.217.77:8898. Q( Q1 b- R9 k( L
years. The island’s jagged edges were created by massive avalanches.7 M* u0 _! N0 S! \8 F; ]
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Augustine 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,bttvb1 g2 H1 G1 V( L+ y( Y0 @; V! w
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
( x- l: m' f* [ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of 5.39.217.77:8898( p- C M) [1 m7 \) ?& P+ P! o2 r
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 5.39.217.77:88989 U8 B. Z1 N' u, i& H4 @+ \, X
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.5.39.217.77:88984 e4 A& V2 s; G0 s/ E
% b5 s* u2 _0 S& b) _The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising 2 S& L& `% l/ ^% j3 j$ F" x* J6 Q& B" @3 q
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 tvb now,tvbnow,bttvb8 J3 T8 t7 a. a
as a pyroclastic flow.
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$ l+ g$ e2 k* ] |* s7 R( vThis photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:3 ^) \! w9 ^6 c. i7 h% D% r$ P
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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.+ g$ r) s0 }5 {, E) `
* A shockwave from the eruption could have blown a hole in the cloud deck.
1 M" v h& ^) `! l; {tvb now,tvbnow,bttvb * 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.
, X$ Z/ E9 Y$ M/ g" I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
0 M- v) j- K; b( J, g9 D4 w公仔箱論壇 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: ~1 O) d' }: l+ S0 F3 J
- Y% G1 T% 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。Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.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。% x9 U9 Y0 J0 C' J6 C$ [
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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! F( l5 }: z3 R; I+ D
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one tvb now,tvbnow,bttvb# r2 X' v) n, P$ Q8 ~! w" }/ t
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
& E+ b* c& t: s# b1 a: o4 wTVBNOW 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。this picture are from forest fires ignited by lava.3 a7 O% f8 w2 v0 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 may5.39.217.77:88989 o) U3 [7 J0 `% F
also be the oldest-known active volcano. h# c* X# {% \ @% ~
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; ^' ]9 k/ Y% |8 @公仔箱論壇A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
5 k* N4 y+ F" i7 O+ T' s3 u3 yand 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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+ B. A1 i+ j+ q, ]+ b公仔箱論壇 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。) ?8 {3 ^2 j4 R! Y/ o" U
\. b0 M& R. }Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. tvb now,tvbnow,bttvb/ V5 A- l! M0 @
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 0 b- v E$ J0 `) \& h
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
3 m5 q, m" M1 u/ U. q9 Tof frequent activity. The plume reached heights of around 30,000 feet.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。/ G M+ m+ x- l, p0 j% s$ c
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% C6 A0 Q) Q" C7 h# W$ y+ dThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 5.39.217.77:8898' i% R, Y W7 g8 C5 H8 `
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
, G0 t. c V7 x- A$ i$ ]0 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。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.4 r6 I+ O! s5 ?8 ]9 K% M
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% |3 g7 b9 M; e; }6 X5.39.217.77:8898This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
$ W' S8 W) z2 A' v. z' ^公仔箱論壇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 5.39.217.77:8898$ v0 L5 L7 Q/ i
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5 `/ h& {; f4 t$ K) P( U3 k# O! O% F
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. tvb now,tvbnow,bttvb5 a: `8 e# j7 {6 q( [% A
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
: E0 {5 _% P/ A: ^. T) Htvb now,tvbnow,bttvbthat 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,
3 d/ }& R7 V; R5.39.217.77:8898causing avalanches of debris into the crater. |