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Masive Asteroid Damage Zone Found: 20 Kilometer Asteroid Caused 30,000 Square Kilometers Devastation
Research from The Australian National University (ANU) has identified one of the most extensive asteroid impact zones on Earth. The discovery came prior to the passing of a 45-meter-wide asteroid very close to Earth on February 15.
Located in northeast South Australia, the East Warburton Basin contains evidence of a 30,000-square kilometre shock-metamorphosed terrain thought to have been caused by an asteroid measuring 10 to 20 kilometres in diameter that hit Earth more than 298 million years ago.
Dr Andrew Glikson, a visiting fellow in the ANU Planetary Science Institute and the ANU School of Archaeology and Anthropology, studied the impact of the ancient asteroid following an initial suggestion by Dr Tonguc Uysal of the University of Queensland.
“The size of the shock metamorphic terrain, larger than 200 kilometres in diameter, makes it the third-largest discovered to date on Earth,” Dr Glikson said.
“It is also possible that the asteroid impact dates back to the late Devonian period – 360 million years ago – a time of major mass extinction.”
Dr Glikson says research into past asteroid impacts is essential in the face of potential future asteroid encounters. This weekend, an asteroid – 2012 DA14 – will pass just 34,000 kilometres from Earth, potentially interfering with communication satellites. If the asteroid was to hit Earth, it would make a crater up to one kilometer wide, says Dr Glikson.
Dr Glikson believes that there may be a link between the East Warburton impact zone and another possible impact site, the West Warburton geophysical anomaly, located nearby.
“Asteroid impacts commonly occur in clusters of two or more projectiles. Where impacts are near-contemporaneous they are usually fragments of a larger body broken under the gravity effect of the Earth-Moon system.
Dr Glikson studied micron-scale features within quartz grains from sub-surface drill holes, using a three-dimensional optical microscope and a scanning electron microscopy. Dr John FitzGerald of ANU studied the features by Transmission Electron Microscope and Dr Erdinc Saygin studied deep seismic anomalies below the structure.
“These methods helped me to discover the impact site, which was buried under nearly four kilometres of younger sediments,” Dr Glikson said.
The finding follows the discovery of a 125-million-year-old impact structure 84 kilometres in diameter in southeast Queensland by Dr Glikson and colleagues.
The research is published on-line in Tectonophysics.
Asteroid Strike in Timor Sea
Previously, in May 2010, scientists from The Australian National University have identified a dome at least 50 kilometres in diameter, buried under the Timor Sea that was created by a giant asteroid that collided with Earth around 35 million years ago – a period of heavy extraterrestrial bombardment.
Their findings, which could suggest a link between these impacts and a sharp fall in global temperatures preceding the formation of the Antarctic ice sheet, have been published in the new issue of theAustralian Journal of Earth Sciences.
Seismic surveys in areas straddling the Ashmore Platform and Browse Basin led oil company geologist Dariusz Jablonski of Finder Exploration to suspect the large impact. Dr Glikson, who is a specialist in the study of extraterrestrial impacts, from the Planetary Science Institute and the School of Archaeology and Anthropology at ANU, was asked to study cuttings from the Mount Ashmore-1B well.
Dr Glikson said “The minimum size of the Mount Ashmore dome, which represents elastic rebound doming of the Earth crust triggered by the impact, is 50 kilometres at the base, but the full size of the impact crater – not yet defined – may be significantly larger”.
“The identification of microstructural and chemical features in drill fragments taken from the Mount Ashmore drill hole revealed evidence of a significant impact,” Dr Glikson said.
Dr Glikson said that the period when the asteroid hit coincided with a time of heavy asteroid bombardment of the Earth, which may have played a role in the sharp drop in global temperatures at the time.
“Round the same time as the Mount Ashmore impact, a 100 kilometre wide asteroid impact structure formed in Siberia, and another measuring 85 km in diameter in Chesapeake Bay, off Virginia, in the United States. Likewise a large field of tektites – molten rock fragments splashed by impact – fell over northeast America. This defined a major impact cluster across the planet,” he said.
“This impact cluster hit Earth about one million years before the Drake Passage, the ocean gap between Antarctica and South America, opened up. The opening of the Drake Passage allowed continuous circulation of the circum-Antarctic ocean current, isolating the Antarctic continent and allowing the onset of its large ice sheet, which acts as a ‘thermostat’ for the Earth’s climate.”
Dr Andrew Glikson said that the increase in geophysical surveys and drilling associated with oil exploration over the last few decades has allowed the identification of a number of large impact structures onshore and off the coast of Western Australia.
Contacts and sources:
Astralian National University
2013-02-24 18:45:26
Source: http://nanopatentsandinnovations.blogspot.com/2013/02/most-masive-asteroid-damage-zone-found.html
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