One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic 公仔箱論壇# U" P, i* {9 W3 ~7 q6 g- B- |
eruptions. 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。* F9 |. B: Z. f7 z2 Q$ _
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.. C8 Z; f3 P! O& }( G! l
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, tvb now,tvbnow,bttvb+ h0 a( K- a8 q, u
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
4 W' O) ?1 G7 v4 p! z3 O* l+ gand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions.
9 K" V5 o) b' D$ ~; I1 e! n0 aThey tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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& n, h" ]: V! W( T$ I公仔箱論壇Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above 5.39.217.77:8898 H- Q) _! E. k
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
p0 ^, s( V, R/ r% Ltaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
6 q# c; C- g' \+ v& F! V4 W4 ~tvb now,tvbnow,bttvbplume reached as high as 50,000 feet.5.39.217.77:8898! A! ]# S0 T( t, v
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra tvb now,tvbnow,bttvb* K# ]1 M3 O4 u3 ]) q4 ^* ]
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000
/ Q3 {# w5 k) n' B& 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。years. The island’s jagged edges were created by massive avalanches.
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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,bttvb3 |- }9 Y" j3 r4 J+ _+ S
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet
( Q5 l* ]; i6 P* l7 f( 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。ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of tvb now,tvbnow,bttvb# R I" l2 ]/ u# n& b
the continental crust, creating magma that drives the volcanic eruptionstvb now,tvbnow,bttvb# W, M6 t1 \$ J4 \
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
# s# }% K) o2 H$ P" Htvb now,tvbnow,bttvbin the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.
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6 i$ }: `7 |* T' A$ {2 J0 q: z' U# |The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising 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。. X# r, w, i9 }% J' b" I1 }; z, 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 9 o1 U( K- o" f$ l
as a pyroclastic flow.
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( O) M Z( s0 AThis photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:5.39.217.77:8898# a2 B$ C# f+ t' f5 _* n, m
$ r3 v. q7 q8 q/ [! A- Wtvb now,tvbnow,bttvb * It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
2 |9 |+ Q- L5 D( {/ W9 } * A shockwave from the eruption could have blown a hole in the cloud deck.
. z7 Y0 a; k3 Y/ o* d, h+ j' N * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.% g$ y5 o& H1 z4 v
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Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
9 y0 i0 |9 Z) J% \tvb now,tvbnow,bttvbIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
k4 \% C& B* B0 x* ]公仔箱論壇 the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.$ F5 F3 x4 b: k! D
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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.tvb now,tvbnow,bttvb# N& X. l1 s* S/ J) \) Y
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4 f z% j' b0 I( i) o4 j公仔箱論壇Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes inTVBNOW 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。% v; |8 |/ l( Y) A, C0 n, O
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
5 Z5 H. z; \5 t) J& I4 ocaptured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
, l7 O5 c$ i+ Vthis 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
0 Q3 Y& R& l* q" i& g$ ]2 w5.39.217.77:8898also be the oldest-known active volcano.$ |9 ~: W$ ]0 M, ]% P# t
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% T" U: P, m3 UA NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high 5.39.217.77:88989 `6 Y" J, q+ Q/ H* n- x
and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.公仔箱論壇9 O4 J! B- ?- @- m
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. % U: L3 c! k2 N0 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
' v4 u3 f# X$ b3 U公仔箱論壇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
, X3 T7 f& w" N+ E' c6 N公仔箱論壇of frequent activity. The plume reached heights of around 30,000 feet.5.39.217.77:88987 k! D& x1 N3 ~( N
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
" q( x5 v5 }: y) Y( ^. ~tvb now,tvbnow,bttvbwest coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.
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6 W' ?. r$ M- O& ~1 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。Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
, |( I& |$ D* }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.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。* o% p9 d/ w* _
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- L0 }8 r. u) j: L$ k5.39.217.77:8898This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra : r# Q7 x8 }/ A
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
; I9 l. n0 Q' `. mformed 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 5.39.217.77:8898. t+ o0 _8 `, I* }% }& \0 ^
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.5.39.217.77:88982 ^0 b; h6 h n7 w7 I% s; ]# N
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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. tvb now,tvbnow,bttvb$ d7 |6 K6 @( p% ?. W/ q+ H
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
% K) C+ M4 o& v0 O* R, G5.39.217.77:8898that 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 l) V$ d1 L; A3 x2 Y( S$ ~' v) b
causing avalanches of debris into the crater. |