One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
7 O: } v; @+ ?) Y, Qtvb now,tvbnow,bttvberuptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
: J& \+ e& J3 g3 Z6 H* Q5.39.217.76active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.
9 R! Q6 ]4 L/ C8 v4 e5.39.217.76Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
k- i k+ w0 H7 p3 {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。erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
* {" \8 A2 V) F, q" s( g/ q2 g公仔箱論壇and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
* x6 S! P2 x" x; u. B: ?6 ^' h! _They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.tvb now,tvbnow,bttvb& Q }6 M4 _1 \$ Z" @7 a
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 5.39.217.761 V& n. M9 Z0 R: a5 C
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas公仔箱論壇9 p( V( F8 K: v8 w5 E; t; [
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash ; ?/ R: y5 U' k7 k5 { G& y
plume reached as high as 50,000 feet.
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5 w5 p, y, W0 F9 g$ d, gAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
9 @8 \. m4 M3 s* ]8 k& F% Q+ o5.39.217.76satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
- y' k& G& k4 w% B9 k! ^5.39.217.76years. The island’s jagged edges were created by massive avalanches.tvb now,tvbnow,bttvb3 I, F4 D) x3 \
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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 tvb now,tvbnow,bttvb4 A3 L( F# u+ B; J, r: P
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet 公仔箱論壇8 L5 ?2 k7 @+ t1 {/ r
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of 公仔箱論壇- @% x# V4 R3 e& K d+ X
the continental crust, creating magma that drives the volcanic eruptions, d$ h2 Q: ~3 q& b( w
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
) H. ]* Y- y+ I0 B- R# k5.39.217.76in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.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。0 [' w7 W; ^2 A
" \" L5 i3 `7 o, 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。The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising
0 G& ?1 @: d2 C$ I4 N5 @. T公仔箱論壇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
( p% H1 A2 X' w& ras 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:5.39.217.76. M+ e4 N& S: o' X' }
) B; u& I4 A( I5 E * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.& l: J) U3 @8 t ^- V1 ^4 V
* A shockwave from the eruption could have blown a hole in the cloud deck.公仔箱論壇; G6 R2 G# ]- q$ s$ f4 y
* 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. ' i% g9 D; R$ v6 |
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when- W2 a: P8 j) \" P
the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.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 W( |+ ^( i
" A4 I' p: v6 X" ^& ?! @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。Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.公仔箱論壇- I ]# `7 ~! W8 y' }; G
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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
( B( M' I8 y9 ~$ f) o" P the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
( Q f$ n) J$ p; vcaptured 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& P! }6 J9 l* W L/ }2 x- G9 D
this picture are from forest fires ignited by lava.5.39.217.768 B8 o2 r, e* O6 J* `, U
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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 maytvb now,tvbnow,bttvb8 R$ E6 v8 p7 B: r: V7 \
also be the oldest-known active volcano.5.39.217.76' u, j" W% w: o' B$ X. [4 D
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$ e* ~" p2 m" g1 yA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high 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 `6 U3 z8 e
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.tvb now,tvbnow,bttvb" {, W$ a5 `% G
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; }! X z; P6 `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。Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
% x- |6 l0 u6 R1 x5 P1 t& y% Ytvb now,tvbnow,bttvbThe 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 7 T7 b3 m& c; O& R
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
5 G& T) `- q6 W' t/ ftvb now,tvbnow,bttvbof frequent activity. The plume reached heights of around 30,000 feet.5.39.217.76/ l: ~; Y4 n* M. U \, r$ B
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
! m* X- k0 Y1 K公仔箱論壇west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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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
# p$ u# s5 u- W# N% V) J# T5 U. jtvb now,tvbnow,bttvbflows 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., Y7 @' V# W* N. I9 l( h; @
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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 tvb now,tvbnow,bttvb7 F- o* F7 V3 u7 T) ]
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
' z$ d9 Q3 s4 C" c9 c9 u& pformed 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。, y* k0 Q% p* I. {
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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5 @3 K' i7 o6 u6 Gtvb 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.
! ~' K7 x: ? k; YA 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
+ o7 X0 x& d2 s' K* f* r( S7 mthat 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,
5 a$ ^$ m, n' i- n C F* Scausing avalanches of debris into the crater. |