Thursday, April 18, 2013

Top 10 Largest Meteor Craters on Earth

A meteorite unexpectedly pierced through the atmosphere over the Urals Region in Russia on Friday morning and exploded about 12 to 15 miles above ground, creating a shockwave that damaged houses, shattered windows and injured more than 1,200 people. According to NASA, the celestial body, which measures 17 meters in diameter and 10,000 tons in weight, crossed the atmosphere at the supersonic speed of 44,000 miles per hour and released a force of 500 kilotons at the time of its explosion, 30 times that of the nuclear bomb dropped on Hiroshima in 1945. Scientists in Russia are still searching Chelyabinsk for leftover debris.

Usually, a meteor crater will be formed when a meteor impacts another celestial body. A number of meteor craters can be found across the Earth, but few have diameters of 20 kilometers or above. Statistics show that on average the Earth experiences only one to three meteorite falls powerful enough to leave a 20 km diameter crater per million years. Following are the top 10 largest meteor craters ever recorded in our planet’s 4.6 billion-year-long history.

10. Puchezh-Katunki Crater
Location: Nizhny Novgorod Oblast, Russia
Diameter (km): 80
Age (mln years): 167
Coordinates: 56°58′N 43°43′E
Puchezh-Katunki is a meteor crater in the Chkalovsky District of Nizhny Novgorod Oblast in Volga Federal District, Russia. It is 80 km (50 mi) in diameter and is estimated to be 167 ± 3 million years old, placing it in the Middle Jurassic. The crater is not exposed to the surface, but appears as variation in the vegetation. The central dome, ring depression, and ring terrace of the 80 km (50 mi) wide impact structure are nearly completely buried under Neogene and Quaternary sediments, with the only exposed impactites found on the banks of the Volga River.

9. Chesapeake Bay Crater
Location: Virginia, United States
Diameter (km): 85
Age (mln years): 35.5
Coordinates: 37°17′N 76°1′W
The Chesapeake Bay impact crater was formed by a bolide that impacted the eastern shore of North America about 35 million years ago, in the late Eocene epoch. It is one of the best-preserved "wet-target" or marine impact craters, and the largest known impact crater in the U.S. Continued slumping of sediments over the rubble of the crater has helped shape Chesapeake Bay.

8. Acraman Crater
Location: South Australia, Australia
Diameter (km): 85-90
Age (mln years): 580
Coordinates: 32°1′S 135°27′E
Acraman crater is a deeply eroded impact crater in the Gawler Ranges of South Australia. Its location is marked by Lake Acraman, a circular ephemeral playa lake about 20 km in diameter. The discovery of the crater and independent discovery of its ejecta were first reported in the journal Science in 1986. The evidence for impact includes the presence of shatter cones and shocked quartz in shattered bedrock on islands within Lake Acraman.

7. Popigai Crater
Location: Siberia, Russia
Diameter (km): 100
Age (mln years): 35.7
Coordinates: 71°39′N 111°11′E
The Popigai crater (or astrobleme) in Siberia, Russia is tied with Manicouagan Crater as the seventh largest verified impact crater on Earth. A large bolide impact created the 100 kilometres (62 mi) diameter crater 35.7 ± 0.2 (2σ) million years ago during the late Eocene (Priabonian stage). The crater is 300 km east from the outpost of Khatanga and 880 km (550 mi) NE of the city of Norilsk. It is designated by UNESCO as a Geopark, a site of special geological heritage.

6. Manicouagan Crater
Location: Quebec, Canada
Diameter (km): 100
Age (mln years): 215
Coordinates: 51°23′N 68°42′W
The Manicouagan Crater is one of the oldest known impact craters on Earth and is located primarily in Manicouagan Regional County Municipality in the Côte-Nord region of Québec, Canada, about 300 km (190 mi) north of the city of Baie-Comeau. At roughly 213-215 million years old, Manicouagan is one of the youngest large astroblemes visible on the surface. Its northernmost part is located in Caniapiscau Regional County Municipality. It is thought to have been caused by the impact of a 5 km (3 mi) diameter asteroid about 215.5 million years ago (Triassic Period). It was once thought to be associated with the end-Carnian extinction event. The crater is a multiple-ring structure about 100 km (60 mi) across, with its 70 km (40 mi) diameter inner ring its most prominent feature; it contains a 70 km (40 mi) diameter annular lake, the Manicouagan Reservoir, surrounding an inner island plateau, René-Levasseur Island. It is the earth's sixth largest confirmed impact crater according to rim-to-rim diameter. 

5. Kara Crater
Location: Nenetsia, Russia
Diameter (km): 120
Age (mln years): 70.3
Coordinates: 69°6′N 64°9′E
Kara is a meteor crater in the Yugorsky Peninsula, Nenetsia, Russia. It is 65 km in diameter and the age is estimated to be 70.3 ± 2.2 million years old (Upper Cretaceous). Impactite outcrops located on the Baydarata Gulf shore north-east of the crater imply that the original size of the crater, now greatly eroded, was 120 km in diameter, making it the 4th largest on earth. The crater is not exposed to the surface. 

4. Woodleigh Crater
Location: Western Australia, Australia
Diameter (km): 60-160
Age (mln years): 364
Coordinates: 26°3′S 114°40′E
Woodleigh is a large meteorite impact crater (astrobleme) in Western Australia, centred on Woodleigh Station east of Shark Bay. A team of four scientists at the Geological Survey of Western Australia and the Australian National University, led by Arthur J. Mory, announced the discovery in the 15 April 2000 issue of Earth and Planetary Science Letters. The crater is not exposed at the surface and therefore its size is uncertain. The original discovery team believe it may be up to 120 km (75 mi) in diameter, but others argue it may be much smaller, with one study suggesting a diameter closer to 60 km (37 mi). The larger estimate of 120 km, if correct, would make this crater tied for the fourth largest confirmed impact structure in the world, and imply a bolide (asteroid or comet) about 5–6 km (3.1–3.7 mi) in diameter. A more recent study suggest the crater could be between 60 to 160 km or more, and was produced by a comet or asteroid 6 to 12 km wide. 

3. Chicxulub Crater
Location: Yucatán, Mexico
Diameter (km): 180
Age (mln years): 65
Coordinates: 21°20′N 89°30′W
The Chicxulub crater is a prehistoric impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is located near the town of Chicxulub, after which the crater is named. The age of Chicxulub asteroid impact and the Cretaceous–Paleogene boundary (K–Pg boundary) coincide precisely, leading to the conclusion that the cause of the crater was the same cause resulting in the demise of nonavian dinosaurs on Earth. The crater is more than 180 km (110 mi) in diameter, making the feature one of the largest confirmed impact structures on Earth; the impacting bolide that formed the crater was at least 10 km (6 mi) in diameter. 

2. Sudbury Basin
Location: Ontario, Canada
Diameter (km): 250
Age (mln years): 1849
Coordinates: 46°36′N 81°11′W
The Sudbury Basin, also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geologic structure in Ontario, Canada. It is the second-largest known impact crater or astrobleme on Earth, as well as one of the oldest. The basin is located on the Canadian Shield in the city of Greater Sudbury, Ontario. The former municipalities of Rayside-Balfour and Valley East lie within the Sudbury Basin, which is referred to locally as "The Valley". The urban core of the former city of Sudbury lies on the southern outskirts of the basin. The Sudbury Basin is located near a number of other geological structures, including the Temagami Magnetic Anomaly, the Lake Wanapitei impact crater, the western end of the Ottawa-Bonnechere Graben, and the eastern end of the Great Lakes Tectonic Zone although none of the structures are directly related to each other in the sense of resulting from the same geophysical processes.

1. Vredefort Crater
Location: Free State, South Africa
Diameter (km): 300
Age (mln years): 2023
Coordinates: 27°0′S 27°30′E
Vredefort crater is the largest verified impact crater to have existed on Earth, more than 300 km across. It was located in the present-day Free State Province of South Africa and named after the town of Vredefort, which is situated near its centre. While the crater itself has long since eroded away, remaining geological structures at its centre are known as the Vredefort Dome or Vredefort impact structure. In 2005, the Vredefort Dome was added to the list of UNESCO World Heritage Sites for its geologic interest.

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