One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
" X4 w1 d* n& S0 qeruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are 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 V# Q( I# N) y* q; n
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.* J2 {/ }' d% L6 V5 x
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
5 v7 e5 s! @7 N! P2 [) 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。erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous 1 f. P. f+ E9 k+ F
and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
7 O5 G t, s$ P* f& a公仔箱論壇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
0 R$ {1 q4 h1 j1 xof Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
" I& ]! b5 O/ J7 L Htaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
, A8 a! ~9 x6 [plume reached as high as 50,000 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。8 n0 b7 Q$ u$ R1 ?8 ]0 G# z* O
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
. n7 ]" b$ {3 N; G' q3 ]& Ztvb 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 # B# c1 l# ^/ I- _+ } O
years. The island’s jagged edges were created by massive avalanches.7 ^# w8 W0 f# G- u
5 E) ?+ b4 S6 }$ v# s# tAugustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring
5 b4 S3 k6 ~0 M6 o0 oos.tvboxnow.comof 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。1 d' H# }! @% ^: |) ?# H: _
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of % [" N% Z8 i# @. L
the continental crust, creating magma that drives the volcanic eruptions- A. \ p4 R! U- M
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano os.tvboxnow.com* T: B* ~* D; d+ T
in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.
' B+ K6 J7 Y( s" H: d3 {, 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。
- {7 P! c: C T& T6 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。The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising ) J4 c6 V9 |. n8 d* J& H3 N2 r
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
4 k6 e1 l( _- C e/ uTVBNOW 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.os.tvboxnow.com4 \9 U+ D. \( z; s c/ I
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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:# k1 u1 r% Q. O+ h; ?! o
0 I7 O% R$ F0 b v * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
! N0 R$ P9 D `4 b) b& Q% fTVBNOW 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.
1 m/ Q U5 F( B# A$ C5 S * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.2 X/ u/ q3 S% R, P! f6 H
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4 L/ ?8 l% ?2 sAlaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. 公仔箱論壇+ G1 T. S, }# }7 X4 K& ^' B0 S
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
& q4 w+ W3 j7 K+ \8 [' Z7 Q+ h+ @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。 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.os.tvboxnow.com" ^3 Z" h: |) ^$ q( [1 u
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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 inos.tvboxnow.com/ ?/ u% k4 B8 z$ d) 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 : |+ i; U3 {4 f9 Y( J* B' s9 I
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in tvb now,tvbnow,bttvb: e0 u3 S3 \6 \, N4 G1 b
this picture are from forest fires ignited by lava.tvb now,tvbnow,bttvb! F4 T/ w+ G* a8 C' j" }, A1 m3 \
. R |0 ~5 f3 J8 aTVBNOW 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,bttvb$ v) N8 v% V7 x8 E- ^
also be the oldest-known active 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。9 \. A& d3 W* k7 D' k
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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
3 p Q0 y; n8 z0 x% sTVBNOW 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.
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. 4 X9 h6 f/ Z8 g$ _/ q5 |; Z% h* h
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
2 e+ v: t2 \- v6 F, c& Y) qos.tvboxnow.commultiple 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 os.tvboxnow.com2 A1 d3 j. F' `. a9 l* e) D" x; T1 N
of frequent activity. The plume reached heights of around 30,000 feet.
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. u8 m0 x9 ]& _3 nos.tvboxnow.comThis eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the os.tvboxnow.com- z* S' U# R) `- W( B A
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.tvb now,tvbnow,bttvb/ D; |$ n# u; t6 C7 r3 s: B2 R( R
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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 2 r. \0 |+ _1 R; v6 ~+ R0 l; H
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.os.tvboxnow.com% K* P* L9 A, c: ?
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# Q4 ]" k% l& _% ^/ `0 o" kThis image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
$ S1 P2 y1 T/ U- y4 T( z+ F9 z! m& xos.tvboxnow.comis 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
- N% Q. K7 e4 T( a, Hformed 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
& U8 ?! o6 T- t. w# X Y公仔箱論壇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.
5 x" @. ]' I- v K; t3 j# t& oA 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
H! T4 O" c. |) ?' A1 z+ STVBNOW 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。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,
/ l9 ?( P \! g3 O公仔箱論壇causing avalanches of debris into the crater. |