One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 2 X0 u* S4 M* _. N
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 公仔箱論壇2 N! Q4 v5 ~; t' k* W' n
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.公仔箱論壇/ i4 j+ C3 |3 V G+ D+ S
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
+ W/ R6 x* d- ]/ Xerupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
9 C( [$ Q# a9 n6 k' q% X/ 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。and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
) f' L2 w( G. c7 Z3 I" x3 M6 A5.39.217.77:8898They 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。; U, ^! I; b/ D8 `
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
' v) f: e: [2 T! h" z2 C公仔箱論壇of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewastvb now,tvbnow,bttvb# Z4 F1 j0 ~1 @7 t: A3 T6 g
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
# U: j4 y3 ]+ s4 {: ^+ O/ ~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。plume reached as high as 50,000 feet.! i- W1 i7 D1 \) R. {; h, q
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- [! M' O' g' Q3 ?) U" m/ htvb now,tvbnow,bttvbAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 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, V% G. Z, R# @6 f1 K
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
2 W- L7 _0 c9 @8 }: `tvb now,tvbnow,bttvbyears. The island’s jagged edges were created by massive avalanches.
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3 W T$ \9 l6 x4 H( J9 _6 r/ O公仔箱論壇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,bttvb" b. k+ c! ^# ^5 q
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet 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。2 t6 z( w( F+ v* |* M
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of tvb now,tvbnow,bttvb3 H7 F+ q% _* @6 N! w- Y. g q
the continental crust, creating magma that drives the volcanic eruptions
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+ u ^ r! R. T4 o! NAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
0 L( f3 F0 }" c, vtvb now,tvbnow,bttvbin 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
8 p( H. y' i& P" OTVBNOW 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 5.39.217.77:8898 n3 j; v4 u5 ?# y, ?# E* A
as a pyroclastic flow.- C4 O+ p5 M0 \% l
* U* t: R; r: m# JThis photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:公仔箱論壇, c+ }$ m" k/ {- x3 ^9 @
* q6 l$ H j) p7 E) ^7 r * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
I& ]- X6 `$ m! _1 N2 \tvb now,tvbnow,bttvb * A shockwave from the eruption could have blown a hole in the cloud deck.
( D! D8 u5 ^/ A; U D# I( N6 ~公仔箱論壇 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.$ b6 |6 r$ Z3 ?% d/ A+ m9 p
5.39.217.77:88987 j/ y5 m0 o4 @8 Y \
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4 X1 P$ Q4 l* v2 h! p3 P: 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。Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
; U: ?# K' [2 `, i C0 H/ LIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when公仔箱論壇( ~$ [% h3 a- b/ j8 C
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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Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.1 G1 e3 V" Q J2 L) 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 in
1 t9 e+ Y4 `4 `( Q 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 x' }) D. {: A$ M9 F5.39.217.77:8898captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
; j$ m5 a# v" e. G# R公仔箱論壇this picture are from forest fires ignited by lava.
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6 @7 H# c" u+ d2 Itvb now,tvbnow,bttvbEtna 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
8 I# E1 [$ x0 |' l% c# W/ Talso be the oldest-known active volcano.' w2 I5 \5 e( @% f3 n9 u) T9 J
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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 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 U/ |$ h; d3 q% ?. S& K0 m
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。8 M; a5 \+ |7 Y3 P5 C
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
+ E# O. T" I8 `& y% i4 a5.39.217.77:8898The 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 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( L( j! J0 V) B
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
: i6 R7 s' ^( Q4 b% B( t' i公仔箱論壇of frequent activity. The plume reached heights of around 30,000 feet.tvb now,tvbnow,bttvb) I( X+ _3 X6 o$ P
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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。# g* f# ~8 C0 p
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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- d0 {0 A' |8 G/ @# A. gChaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
, D0 F$ Q" |% w# z5 M+ i. p3 x5.39.217.77:8898flows 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
1 A) M+ B K. l$ T8 a* y4 F* C6 bis 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/ W! N2 m( Q/ {7 Q$ u3 iformed 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
& \& W- Q) M9 t6 a) `stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.+ V* ]+ V) {1 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% [7 q- m7 r o4 @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 . N2 j1 T9 a7 N7 N% i2 y5 }
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, 5.39.217.77:8898( N( Q% Q1 ~) m' N
causing avalanches of debris into the crater. |
發表於 2009-12-22 08:34 AM
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