One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic tvboxnow.com6 D! e2 b# G# [3 u/ ?
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
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Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, 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。# F0 c# v5 b8 t4 s! E. ~# Y0 x% [
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
3 C$ S! x& S0 @7 |公仔箱論壇and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. . e8 E ~7 L* Z3 ^1 @" P2 @
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.tvb now,tvbnow,bttvb- z W' C- z; u" ^/ f& H# U1 a! ` a
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u8 \: P) [/ t0 t2 F9 A# Otvb now,tvbnow,bttvbMany of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
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taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash tvboxnow.com8 e' c4 p7 M% q9 |- m* R0 E
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 / _# h. p8 X& \# u+ H2 H1 s
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
0 ~8 F" T, l" syears. The island’s jagged edges were created by massive avalanches.
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, p$ @ d7 Q9 W; iAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
/ ?/ V" f1 x! A7 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。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。4 ]& x; k! j; X/ W3 ]
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of tvb now,tvbnow,bttvb0 c. C/ I5 [( C6 ^
the continental crust, creating magma that drives the volcanic eruptions
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1 K' M- Z+ C* ?* Etvb now,tvbnow,bttvb
" U0 T A4 Q) w* 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。Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano tvb now,tvbnow,bttvb8 H7 p. p6 c3 w8 i5 {) t' z
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.
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$ L. n3 o" T/ O' j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
1 G" C" V1 C8 |6 c! mand 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。: K* P+ R% l. U p8 r3 x% z3 Z
as 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:
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2 o* ~, j. n- z, x0 J; X公仔箱論壇 * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
, Z( G6 i/ u& L2 m1 |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。 * A shockwave from the eruption could have blown a hole in the cloud deck.tvb now,tvbnow,bttvb$ i4 O( W% f+ L6 j' E8 w
* As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.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。* Z4 _9 a. ?7 v: ^1 F' v" P
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* F+ q+ h5 ?* c, G* |公仔箱論壇Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
1 X0 {$ \, f! ~4 S/ S! H: o0 A. |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 whenTVBNOW 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。3 p* \4 I: E4 @, d8 A5 N
the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.! z) c$ r! @7 b. q
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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 u4 V/ g. n% Q8 q% n/ D- i
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; b3 B7 r. m4 ]" a. Y& x2 dtvb now,tvbnow,bttvbMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
1 C7 R! a2 h4 v) C) [/ Btvb now,tvbnow,bttvb 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3 E+ k+ P: O v7 V3 t2 x
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
% J! C8 n% [8 q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
, V: A. u5 U5 E1 @7 ^1 k# halso be the oldest-known active volcano.
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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
Y* S3 T# n* F! K: y% I H8 zTVBNOW 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 claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.tvboxnow.com4 k' @+ U4 a3 H9 ^- ?- u
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. d7 t' w. ~. P1 H0 \2 ZPopoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. tvb now,tvbnow,bttvb6 Z* R* X5 Q; ~! } J. T
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 tvboxnow.com8 Q9 Z4 J3 d% F8 U" s: N( 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 - {* h3 z7 n" `& Q, l/ x% `4 |
of frequent activity. The plume reached heights of around 30,000 feet.
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3 n4 r8 n2 C0 ^9 W8 htvboxnow.comThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
1 Y* [" y Q& S1 @) ^tvb now,tvbnow,bttvbwest coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.* m4 D2 ~ b0 T* S D
- j1 W6 z) Q) _% o, j% 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。Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
& P8 m- s$ h* P8 Gtvboxnow.comflows 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.tvboxnow.com" z7 k% L' |3 p1 c' I
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7 o9 ~+ m! R' I) {3 Ftvboxnow.comThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
k- P5 x' e. y! x! Q& {5 n. zis 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 tvb now,tvbnow,bttvb/ V }$ T3 c7 z3 e! O/ P
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
! E1 \: H/ z( r/ O; I: T9 O9 @; ~" YTVBNOW 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。stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.tvboxnow.com5 E+ ?. K- G, e. F
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8 C+ @) _1 a/ D y9 c' }tvb now,tvbnow,bttvbNASA’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. 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 b5 d* p4 i; y0 b: m' ~" X' q; q
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 3 w+ |- Q5 S3 ]) m# ` T
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, tvboxnow.com& N2 z8 C# n5 h2 m# L% y
causing avalanches of debris into the crater. |