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Asteroid impact craters are among the most interesting geological structures on any planet. Many other
* Q5 W* C% f+ t. N7 ?& k+ pplanets and moons in our solar system, including our own moon, are pock-marked with loads of craters.
" J- X$ W6 k( H" w4 T- v: G: Y/ GBut because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic 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。+ @: B1 ?) N0 x# F, N) }
eruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact 5.39.217.77:8898* Z: j+ h1 v6 \6 t& R" d
structures don’t last long and can be tough to come by.
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" B# c E. D" z/ L( aBut on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved. 5.39.217.77:8898. A! Z7 z9 `; N% c
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here 公仔箱論壇, L e7 b1 e% G& j: V
show some of the biggest, oldest and most interesting impact craters on the planet.
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Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks 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. B U: l. w( s! V+ F
in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million tvb now,tvbnow,bttvb9 F3 i0 u7 c$ V9 o$ K6 y6 ]
years old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent 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。; `: G. X4 a6 u5 b) n0 M& q" g
unidirectional wind. The image above was taken by astronauts in the International Space Station in July. 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。) p3 | a: I% Z6 l$ h; o
In the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters.5.39.217.77:8898$ l# H/ A0 `0 q. k( M! H
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The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary
% I- r- _" a+ ]- c2 w" F5.39.217.77:8898geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it
! @6 t. z2 Z7 C- w0 o: N! V0 Scould be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are ' n7 Y: x+ ^' }. @: T8 U r, x
seasonal salt-water lakes. This image was taken by the Landsat 7 satellite.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。5 ]( M4 ~* X, j: x: H6 C9 P
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The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred
9 T* S% z& K: a, G4 A' g, gTVBNOW 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。around 210 million years ago at the end of the Triassic period and may have caused a mass extinction that killed around 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。, u8 `9 Z9 C. F
60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide
3 k& r& f" d$ F- Z' }2 Q+ W7 _tvb now,tvbnow,bttvbimpact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a 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。) T9 ~& O: {! z2 p; G7 s7 d2 C2 ~; P
reservoir and popular salmon fishing location.
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This crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was tvb now,tvbnow,bttvb' u4 h: n2 n. @# ^: e2 G
an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy
$ M3 e( T5 {0 p' J" `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。looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood
6 z/ e8 s. d" @4 s; k3 F1 \the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million
( G: M$ `4 c# q" l. \/ y$ }公仔箱論壇and 900 million years old and the raised area at its center is around 1,600 feet wide.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。& Q' r% t/ ~ d+ u% J
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The image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on
2 T$ X2 s' e+ f' \1 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。NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellite9 B. F2 ~) h' C }4 g1 @: _9 |% Q- Z
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The Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the
) I \+ ~( T/ I2 _ O ycenter of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding # X6 n. O9 l; Q [) m- z
grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.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 Q6 G8 ?1 \; m# G9 \7 O3 f8 N1 Y
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Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred
4 z+ p5 k/ {# F8 \" [$ \tvb now,tvbnow,bttvbsimultaneously around 290 million years ago. The larger crater measures 22 miles across.
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The Roter Kamm crater in Namibia is hard to see in visible light, but shows up more clearly with imaging radar. The crater’s
4 [0 l' e4 J/ z5.39.217.77:88981.5 mile-wide rim stands out as a bright ring in the lower left of the image, which was taken by a radar instrument on board
/ s! d6 p; b1 A3 w' f& Atvb now,tvbnow,bttvb the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the 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。: C1 `, L1 G8 D8 m# P" A
photo is a rocky hill, the darkest areas are wind-blown sand dunes, the blue around the crater’s rim may be material that was tvb now,tvbnow,bttvb" W% l, Y& K0 b3 m! m3 E
ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred
& a2 O8 h/ G; z, K4 i2 BTVBNOW 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。around 5 million years ago.
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The Lonar crater in Maharashta, India is around 6,000 feet wide and 500 feet deep and contains a saltwater lake.
2 ~& _$ F' f7 h5 stvb now,tvbnow,bttvbScientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite,
6 H1 g$ L1 D9 L. [a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 years ago.
! h: a, v! `9 u1 e0 i( ^公仔箱論壇This image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s
D' F; x! Z' ^3 E) OTVBNOW 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。Terra satellite. It is a simulated true-color imagetvb now,tvbnow,bttvb/ {5 a6 N; t8 |. x t2 [
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The Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. 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 E; j0 ?+ l; ~. G6 C! D" }
The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.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。) h0 z5 E5 [5 a9 M1 W5 n" g
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, [3 v7 Y- u# ], r2 Utvb now,tvbnow,bttvb5.39.217.77:8898 r; P- m/ |8 j: r- K a- A1 | }. S
tvb now,tvbnow,bttvb# `- a3 j% l2 M4 H$ p9 B1 R
$ m) g# U: `' Q. eTVBNOW 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。Artist’s rendering of a space object or phenomenon, so we couldn’t resist this beauty. This is one man’s idea of what 公仔箱論壇1 T; l! L7 D2 ?& M D- O
a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. + M) E" v1 h( k* Y( t
Fortunately, NASA says nothing this big is headed our way anytime soon.
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