One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
# d" J/ R. Z, D# stvb now,tvbnow,bttvberuptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are tvb now,tvbnow,bttvb* ^2 W7 q3 n: K& {
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
6 ^: k) P3 t. ^' W: n0 B1 O5 z' @公仔箱論壇Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
, }# e0 P5 l4 i6 X/ Herupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 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。" L7 w1 L4 d' O6 Z! W
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. tvb now,tvbnow,bttvb$ t& r' K! T1 \- v6 p t+ A
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。7 b; V2 J6 w* w% g
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4 ~; H @1 u% h, t) I. bMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
" F- Z& C ]# ^of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewastvb now,tvbnow,bttvb1 E# H& A5 i" t4 e
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash 5.39.217.77$ c" h' q L, a
plume reached as high as 50,000 feet.
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
: k9 J, n6 I. \6 m5 hTVBNOW 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。satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 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 x+ P' S7 s% v, }4 o( l
years. The island’s jagged edges were created by massive avalanches.
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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 3 ~, v% z- H2 S! ~$ O& M) x( M
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet 4 |, h4 k, o1 S* M
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
# D: W2 K- v( z2 F- E) R5.39.217.77the continental crust, creating magma that drives the volcanic eruptions
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+ `4 k' ^& j3 ]9 ` 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。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。* w, c w/ M5 U# X5 S
Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
% V# t8 x/ Y* q ^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。in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.5.39.217.778 T& v3 x5 f7 I3 r2 V
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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 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。6 A2 j: @- @' \9 ~0 B% s& }
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 1 q/ g# i% y# w
as a pyroclastic flow.
# A. G* A9 d* o6 \3 ~* 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。
e* c4 l+ c" c3 O1 [: m" Etvb now,tvbnow,bttvbThis photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:
' M1 q) N& n, Y$ p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。6 \8 H$ P' R: n; E7 `- Q
* It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.! ?; C# }+ c, z* R1 S. N1 N* \
* A shockwave from the eruption could have blown a hole in the cloud deck.公仔箱論壇% A. W$ {: t) F& |2 Y$ i) i: O7 X
* 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.
E6 f) }* A: D5 \" Z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
- c) w8 `5 F9 X2 q. ^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.
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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.
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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
4 H6 n. X$ t* R the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
x4 b; [1 W, h. P/ |& \5.39.217.77captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
4 ^: G6 G' Y+ W4 E' {. \公仔箱論壇this picture are from forest fires ignited by lava.
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; `2 B) r i0 S4 f r- ]: PTVBNOW 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。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 maytvb now,tvbnow,bttvb7 i8 v+ S2 T! b6 L
also be the oldest-known active volcano.9 {2 N' I: B, C
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& @- C i0 F3 ^1 b$ ?7 D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 5.39.217.77/ l* Q) t+ H3 N3 R+ T
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.; Q. X2 h- `2 K0 r" @' X
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J1 S. b0 u4 f7 |& }0 z! B7 F$ y公仔箱論壇Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
0 K& Y8 R/ N* k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 . b5 D/ Z y6 t% J+ w
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
' b, |1 O% y7 L; q$ C( ?tvb now,tvbnow,bttvbof frequent activity. The plume reached heights of around 30,000 feet.
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the * g# o, j& r7 ^. a1 }% i2 p( M' o
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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( @% {1 a0 J h _Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic ! y. N$ U8 c+ C8 `5 S
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.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。& ^: F' W# |3 Y. b" ?. a& w7 q
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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 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 J+ U- @, k0 S0 [( D# b
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
. D1 R6 C- s' R1 f3 W2 wtvb now,tvbnow,bttvbformed 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 0 g2 w l$ M* {1 w( w8 t8 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.
- [4 q5 B# E, q _, A1 p7 e5.39.217.77A 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
0 l* T. H/ ^. P1 d4 |0 v" mtvb 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,
+ T$ t- n+ c( I' m; U1 x公仔箱論壇causing avalanches of debris into the crater. |
發表於 2009-12-22 08:34 AM
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