One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
7 O2 N. z. e; Y( J. W Oeruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
+ P) ]4 X( {4 Y6 ^; A5.39.217.76active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.tvb now,tvbnow,bttvb& q$ X; D* a3 {# \
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, ) X7 \- `: [5 h) q7 D) A( A3 B4 A
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
6 V- q b! l* d, [' ?tvb now,tvbnow,bttvband explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. tvb now,tvbnow,bttvb' f2 h5 d1 z( k& Z9 q: E
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 tvb now,tvbnow,bttvb4 n) @1 P. Z9 e Q, g; H
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
9 [1 E: R w) Q. @+ e8 ^公仔箱論壇taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash 公仔箱論壇5 t3 z" A1 l$ q3 U# @6 A4 l5 r% i0 G
plume reached as high as 50,000 feet.tvb now,tvbnow,bttvb) M2 {, [' f! c* g8 R+ Q7 J
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra , c' E9 X1 ]$ Y- ~) m( B# `
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 5.39.217.768 y. z% d$ R0 Q1 Z$ g- U+ \- {, Q
years. The island’s jagged edges were created by massive avalanches.
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8 ]: g5 r# p$ h aAugustine 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,bttvb) w$ ? R E" p4 }8 |
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
! X, B# B9 ]0 pocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of tvb now,tvbnow,bttvb% A1 i* P4 ~$ J" v5 P% x
the continental crust, creating magma that drives the volcanic eruptions公仔箱論壇! q; g: q+ Z7 ^5 I+ Y$ z+ |
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano " d) m# |! w& ~: b0 c
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.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 N' @$ g) _% r6 W: h' }2 t9 X
4 g+ R- N. ^3 w& x& I9 u5 i公仔箱論壇The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
- s2 k3 F" f2 G+ T5 L: U) a$ Y1 t+ Land 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
9 D( Q- x2 h: A1 ras a pyroclastic flow.
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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:& |# E5 d8 ~ |) A
5 {% J$ _4 Q# q" l w* @& j8 v, Ztvb now,tvbnow,bttvb * 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! w2 `. n& L) ~) c7 u4 D& F
* A shockwave from the eruption could have blown a hole in the cloud deck.3 D! ?) s$ \- w
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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" j) Y, i. m* y( I8 f- t6 q7 _6 o5.39.217.76Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. 公仔箱論壇; ^: b& t" h- x& a
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when8 G; ]/ S. o# H0 x' l. i
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* T0 e9 N: f+ f+ M
7 S3 `: T0 P0 w# E) u- i5.39.217.76Redoubt 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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6 I3 t1 S+ e: e0 gTVBNOW 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,bttvb5 Q% ]! e. M0 Y' T: p
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
3 \& j0 v0 K8 n5.39.217.76captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
% f4 A. j: X p, p公仔箱論壇this 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$ [1 R- e. h) v. [: Btvb now,tvbnow,bttvbalso be the oldest-known active volcano.$ a/ {& [! f h1 p3 |
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, B$ e: f* o! i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 公仔箱論壇* c4 l5 h; J( R. ^2 g, H, |
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.
8 u1 q! H, g# V; V% q2 m! @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 + Q6 l1 q0 T+ R5 h1 ^ A; ]
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 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。; E! W( w/ c( Y1 C* H' C0 \! P
of frequent activity. The plume reached heights of around 30,000 feet.
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- D0 _7 G" k" @This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the 公仔箱論壇' H! F, x9 d: G
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 5.39.217.76/ j, v, F7 o* Y0 D% E8 [
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 tvb now,tvbnow,bttvb* D) Z1 A8 S; e) `7 F$ F6 O
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
. O' [8 M7 d7 Y9 ~+ |% M) Hformed 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
* d& e9 `& ]# q ] F; Gstationary 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.
8 T3 C" [5 i& _) d5.39.217.76A 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 , h2 h I) t \7 [
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, , W+ k5 q! r0 S0 d
causing avalanches of debris into the crater. |