One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic tvb now,tvbnow,bttvb" r9 s4 C y5 B8 h4 T; h6 d
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are tvb now,tvbnow,bttvb+ u) Y; R9 S- u" m7 X5 K8 @
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
* Z, p2 S! {: X# nTVBNOW 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。Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
& b: U6 P& [$ Y7 p f2 C" q& jerupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
( D6 x. _6 B4 L! s0 M公仔箱論壇and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. 公仔箱論壇 g' A/ B* ^% S* p
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 tvboxnow.com* Z6 k' n: f: c! F0 u
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
6 b$ o; q; w2 t; I7 P; j# N9 `* 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。taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash # M" y, S7 k4 t. @2 d
plume reached as high as 50,000 feet.
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$ N* A1 X1 p. c, [' e, S/ O6 utvboxnow.comAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
$ D1 H5 {/ o2 M. @# Gtvb now,tvbnow,bttvbsatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
; I5 n( N- v4 h+ V% g2 e2 {4 ~% Kyears. The island’s jagged edges were created by massive avalanches.tvb now,tvbnow,bttvb' Z* _3 v3 V! q( z# [8 J* L8 b
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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
! P @3 Q9 h" q2 n, V) }of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
* D0 V: U- J/ S! w( Rocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of ) M9 p, [4 |8 }
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
$ [: D8 _: y0 Q- \) g) f2 ntvboxnow.comin the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.tvb now,tvbnow,bttvb# R) R3 @" [1 k' N4 H: d
' Y: M& Z; ^8 ]tvb now,tvbnow,bttvbThe smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
8 D% O/ l* ^6 k) r7 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。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 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。" j2 v9 x) o0 Y! B( i
as a pyroclastic flow.
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) i z) o3 \" L; cThis photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:tvb now,tvbnow,bttvb6 T0 Z6 r! J, ^/ Q# i3 f; i, b5 ?7 E
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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.
4 F4 P2 C( o- S" D8 W, M ~公仔箱論壇 * A shockwave from the eruption could have blown a hole in the cloud deck.
n2 {. y$ A$ ?8 ~! 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。 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.公仔箱論壇8 K' U( S' y8 D+ C; R
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4 Y C4 `+ S4 E! a; U9 ktvb now,tvbnow,bttvbTVBNOW 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。$ l/ o% L& j/ p" [% k; l2 r( \
Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
, Y" I6 R ~* M. \1 `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
+ w! K) P) @4 G1 J! s) V% W the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.8 l9 o+ R8 D; D% [0 X4 g2 V
# _- O0 `6 }. e6 htvboxnow.comRedoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.8 a4 X- M) _# J* x- S8 _2 k
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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 intvb now,tvbnow,bttvb2 l9 |5 p7 l+ u% S9 k
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
# C4 T; ~6 X, N9 M- S9 n0 } ptvb now,tvbnow,bttvbcaptured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in * S5 R$ }$ o, q+ v, S+ h2 H# ~9 z
this picture are from forest fires ignited by lava.
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$ o( t# W* [3 {# v1 F9 sEtna 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
, o5 g7 O% z/ J8 l- h& S公仔箱論壇also be the oldest-known active volcano.公仔箱論壇( f8 S$ C+ S8 o: j6 u
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Q( S9 @. d1 ktvb now,tvbnow,bttvbA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high 0 K4 B9 n% H% o- i4 |
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.& \% f" M, o2 Y. k8 Y% L. L# ]
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
) r. n! d) @& M8 o7 e4 C: SThe 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 K6 [6 Q( j! A0 w% _* TTVBNOW 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。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
: ^4 h$ W' T% _0 b. Z. D6 Mof 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。, c( G" B3 V1 p1 e, I$ f
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6 h- l" o: K+ z) ?& X; d! MTVBNOW 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 eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
3 V. h! R. ^( B$ P( Q jwest coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.1 t4 }; i7 v ^5 m
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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 # x' \7 a' Y5 Z* q/ U; b6 n* ]
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.公仔箱論壇- g7 p; W/ ^. s3 U" x* Y. `1 t
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( `) r1 e4 _7 Ctvb now,tvbnow,bttvbThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra tvb now,tvbnow,bttvb6 O; D3 M- F. Z) L
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
# w5 q& y" e7 i( S+ ]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。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
% J7 A) F0 B( a( k! x4 tstationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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2 V3 e7 y0 F1 G7 |: C6 Z i公仔箱論壇 公仔箱論壇1 |* b( ^3 D! _4 E
. Y' W! E6 ~' u& `4 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。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. 公仔箱論壇5 |0 I$ O1 z/ d& ~, T& t6 s
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
6 ^6 j f' k w; Ktvb 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,
( [9 C% t. }. u; j+ Hcausing avalanches of debris into the crater. |