One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic tvb now,tvbnow,bttvb& z. L# ?/ m% u& n
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 公仔箱論壇3 g$ f: G3 |0 `! a h$ m/ ~; G8 {2 W
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
5 x* d% x4 ^8 _+ W' x公仔箱論壇Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 公仔箱論壇) w" S! I4 x0 r4 G, l! g2 Y& ?# \
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous www.tvboxnow.com- o5 I$ |1 e9 k: ]) h! I
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
0 _* n/ j! J( k3 EThey tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.; Y) r3 ^( z. y: J2 p. f( e
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3 ~$ e# t! U0 u2 q1 z5 c( [) yMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above ! b5 ~, D% d4 Q8 S0 ^$ B
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewastvb now,tvbnow,bttvb3 p8 t9 O, _/ {7 W( q5 g! e% C
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash * K+ o. m1 ~4 z7 g: V. U* ~) a' [
plume reached as high as 50,000 feet.
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$ E5 L+ W5 }. Y$ q7 b& f0 A公仔箱論壇Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
# F4 C! e h4 _5 c* F2 M) Bsatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 , u$ \' o+ x- h2 g2 a, `: v {
years. The island’s jagged edges were created by massive avalanches.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。1 \2 x2 c7 ^0 C0 i! N0 `* \
% V4 z6 Y4 V7 k3 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。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" w7 ^: U* ?8 [- |
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。% x5 ~( l, w5 A" |% N
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
f7 w4 u- u; B0 Jtvb now,tvbnow,bttvbthe continental crust, creating magma that drives the volcanic eruptionsTVBNOW 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" S1 U. x7 \- g+ C% l9 d4 ~
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% B$ M6 s2 |6 i2 iTVBNOW 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。Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano ( M: n0 R4 J/ z6 d
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.tvb now,tvbnow,bttvb8 B/ |, l- T3 x! {) Z9 j- @
* U! T+ b1 i; B2 kwww.tvboxnow.comThe smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising tvb now,tvbnow,bttvb6 T. H" i& J% b2 E7 w% B0 v
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
3 A) S: q# ]0 F, c9 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。as a pyroclastic flow.
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, s# A4 `4 [2 q6 k公仔箱論壇This photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:
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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.8 Z4 l( E& \2 X# w% K4 z4 f
* A shockwave from the eruption could have blown a hole in the cloud deck.www.tvboxnow.com: @6 K. c) U" l- c- {( @, n
* 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.
8 y) d5 w1 n K" L" j: Swww.tvboxnow.comIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when1 X) T0 r* q6 U1 L" y" D
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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4 B% ^( R2 b+ G- c+ l公仔箱論壇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
/ I' w5 ^$ I- P- g& w the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 公仔箱論壇0 W: X7 [% w: N$ q9 v) y
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in www.tvboxnow.com4 x$ |0 o# @. q7 L; o
this picture are from forest fires ignited by lava.公仔箱論壇$ y# z: ~. R8 _, V% i$ j
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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
' W7 [. L0 u& W; Q* S: 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。also be the oldest-known active volcano.www.tvboxnow.com2 N: W2 t6 |% H7 G
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( w7 f D- H& i: j3 w1 G! u. }5 YA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
9 |8 o8 {: Z: a- [2 J; Cand claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes./ n5 q9 h. `- C! {: _1 N* K
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9 c! _% x; F) G2 kwww.tvboxnow.comPopoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 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 N$ J- B0 f, I5 `9 \
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 6 ^2 \5 ^2 Z+ J1 J" O% c2 b% i! ?1 y' Y
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 J' s! P: o# U! ]4 A公仔箱論壇of frequent activity. The plume reached heights of around 30,000 feet.
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# G# d& @& h4 WThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
" ^) @7 m9 e6 a# ~" O/ Wwest coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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/ j. N) g* j, g1 R3 }2 U2 @Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic tvb now,tvbnow,bttvb0 {, T# P2 z Q
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
G5 c$ O! h! eis 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
: A9 u0 [; ^9 f1 e! y- S, Yformed 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 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。- I& o# x: }/ s0 _% g
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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2 n; D, ], H1 @: L) q4 S公仔箱論壇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.
g4 A- { t9 o8 p! Z3 y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 tvb now,tvbnow,bttvb+ ]4 V0 q( `) I2 A
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, www.tvboxnow.com0 E% \0 u3 h4 G7 _# z, z
causing avalanches of debris into the crater. |