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3 N, p8 v' [; H6 Y: N5 _2 m" M公仔箱論壇Asteroid impact craters are among the most interesting geological structures on any planet. Many other
6 r2 s2 I4 h3 {7 c& I7 l公仔箱論壇planets and moons in our solar system, including our own moon, are pock-marked with loads of craters.
# v% d8 i! g8 `+ o' Fos.tvboxnow.comBut because Earth has a protective atmosphere and is geologically active — with plate tectonics and volcanic
3 R/ z h# t) A* b; p' [os.tvboxnow.comeruptions, mostly relatively young oceanic crust, and harsh weathering from wind and water — impact tvb now,tvbnow,bttvb* Z: \7 ]! I% _% W% b6 s, B9 c. _8 `
structures don’t last long and can be tough to come by.
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But on a few old pieces of continent, especially in arid deserts, the marks of asteroids have been preserved. 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 y9 Q$ \- y6 q* ?* z$ ]
One well-known example is our own Barringer crater, also known as Meteor Crater, in Arizona. The images here
# Y" J$ @, }+ J Q! B. X/ {$ Nshow some of the biggest, oldest and most interesting impact craters on the planet.% B% e2 q" A* q. x8 H8 B
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Aorounga crater, pictured above and below, is one of the best preserved impact craters on Earth, thanks ; [" X% d4 r8 B
in part to its location in the Sahara Desert in Chad. The 10 mile-wide crater is probably around 350 million
7 X- j5 a/ B5 |1 x9 W* v" ^% Atvb now,tvbnow,bttvbyears old. The stripes are alternating rock ridges and sand layers, known as yardangs, caused by persistent
1 h* n* ]. Y) t- i. j8 s3 K/ u# Runidirectional wind. The image above was taken by astronauts in the International Space Station in July. H. M$ ?4 n3 u' N5 H; Y/ D
In the radar image below, taken from the space shuttle in 1994, reveals that Aorounga may be one of two or three craters.
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The Shoemaker crater in Western Australia, formerly known as the Teague crater, was renamed in honor of the planetary 公仔箱論壇5 F: J$ T2 z4 Q8 }8 P/ Z/ y3 ?9 O
geologist Eugene Shoemaker for whom the Comet Shoemaker-Levy 9 is also named. The age of the crater unclear, but it # b b! ]2 n8 I- \6 m9 ~
could be 1.7 billion years old, which makes it the oldest known impact in Australia. The brightly colored splotches are
* ^9 i. R; E" p0 q5 i0 _1 [tvb now,tvbnow,bttvbseasonal salt-water lakes. This image was taken by the Landsat 7 satellite.公仔箱論壇5 ?! g8 R. t* s; R7 ~& k
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The Manicouagan Crater in northern Canada is one of the largest impact craters known on Earth. The impact occurred
$ A6 I% C% a9 X& H* l% j! m: Rtvb now,tvbnow,bttvbaround 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。9 I; t6 O' ?! h0 V+ h0 j
60 percent of all species. Though the crater has mostly eroded, Lake Manicouagan outlines what is left of the 43-mile wide 公仔箱論壇 x7 \: F+ n0 _4 X5 j' l1 ]5 E
impact structure. The asteroid that created the crater is thought to have been about three miles wide. Today the lake is a
$ i5 e: m1 b0 K7 ~公仔箱論壇reservoir and popular salmon fishing location.
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( A; M8 ^# d8 J, A# t9 L2 xThis crazy looking structure in Western Australia is called the Spider crater, for obvious reasons. Geologists determined it was
/ c# ]- `, U$ h3 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。an impact crater when they found shatter cones, telltale cone-shaped, grooved rocks found only around impacts. The crazy os.tvboxnow.com+ J/ B! ?4 K! m2 K+ |
looking legs surrounding the impact are mostly due to erosion of different rock layers. The harder sandstone ridges withstood
6 W( X( k! Z; x8 y公仔箱論壇the weathering of wind and water better than the softer intervening layers. The crater is somewhere between 600 million
2 v; Q8 E0 x/ G1 v0 `; qTVBNOW 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 900 million years old and the raised area at its center is around 1,600 feet wide.
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5 c1 u9 O8 S d, Dos.tvboxnow.comThe image above is a false-color image taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on & ^. M7 ]* t7 \
NASA’s Terra. The true-color image below was captured by Taiwan’s Formost-2 satellite
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The Gosses Bluff crater in Australia’s Northern Territory sits between two mountain ranges. The raised circular feature in the
5 f5 I! y- S( T$ `os.tvboxnow.comcenter of the structure is around 2.8 miles across, but the original crater rim was probably at the edge of the surrounding 公仔箱論壇$ D' U+ k; L w& S
grayish area. The crater was formed caused by an asteroid impact around 140 million years ago.
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Clearwater Lakes in Quebec, Canada were formed by a pair of asteroid impact craters. The impacts probably occurred
% x5 [5 x t; v6 |. d, C' }tvb now,tvbnow,bttvbsimultaneously around 290 million years ago. The larger crater measures 22 miles across.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。( P E: _, {( C
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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 R# G" s1 s& P
1.5 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! J" O9 o0 ^ I4 Z. b
the space shuttle. Irregular surfaces show up brightly and smooth areas are dark. The white splotch at the bottom of the
" s% Y- H& q. ~8 B \+ 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。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 * M( {0 _; B/ t9 L: ?+ U
ejected during the impact, the red is limestone outcrop and the green areas are mostly vegetation. The impact occurred
; \; A7 E/ l' s- l; N公仔箱論壇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.
; _4 v0 X, _+ [公仔箱論壇Scientists determined the structure was caused by an asteroid through clues such as the presence of maskelynite, 6 N5 |. d* `0 g( Q
a glass that is only formed by extremely high-velocity impacts. The impact occurred around 50,000 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。/ s2 m$ c* k# U6 z1 T4 j2 Q1 X
This image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on NASA’s
, O$ ^+ z9 ~$ m! J$ F2 u0 ntvb now,tvbnow,bttvbTerra satellite. It is a simulated true-color image
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The Vredefort Dome in South Africa is possibly the oldest and largest clearly visible asteroid impact on Earth. * c" U1 }2 R4 i2 w! p' r0 S
The 155-mile crater is approximately 60 miles southwest of Johannesburg and was formed around 2 billion years ago.
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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 J8 h/ P( b$ f
! c4 ]$ B0 |# V8 F7 Sos.tvboxnow.comArtist’s rendering of a space object or phenomenon, so we couldn’t resist this beauty. This is one man’s idea of what ' H' P" J, @ n/ \, n/ _
a 300-mile wide asteroid would look impacting Earth. This event probably would have killed everything on the planet. os.tvboxnow.com; @9 l* t R" @& y& d! |$ R
Fortunately, NASA says nothing this big is headed our way anytime soon.
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