<p>A big asteroid strike dating back to over 300 million years left a huge impact zone in Australia, and changed the face of the earth forever, a new study has found.<br /><br /></p>.<p>The impact zone, which centres on the East Warburton Basin in north-eastern South Australia, was caused by an asteroid up to 20 kilometres-wide that slammed into the planet between 298 and 360 million years ago, researchers at Australian National University (ANU) and University of Queensland have claimed.<br /><br />Terrain around the impact site shows evidence of changes caused by shock-wave related deformation and heating of the ground by an impact event, Andrew Glikson of ANU was quoted as saying by Australian Broadcasting Corporation.<br /><br />“This shock metamorphic terrain covers an area of over 30,000 square kilometres making it the third-largest site of its kind ever discovered on earth,” Glikson said.<br />To confirm the area was an impact zone, Glikson and colleagues studied quartz grains retrieved from drill holes.<br /><br />Optical and electron microscopic examination revealed tiny fractures, which indicate the quartz grains had been shocked by an asteroid or meteor impact.<br /><br />“This is the only way these features are formed,” he said. Follow up observations detected deep seismic anomalies below the terrain where the samples were taken.<br />“This allowed us to determine the scale of the impact site which is buried under four kilometres of younger sediments,” Glikson said.<br /><br />He said that there is a link between this impact site and three or four other large impact sites of the same age scattered around Australia.<br /><br />“Asteroid impacts commonly occur in clusters of two or more projectiles,” he said, adding “Where impacts are near- contemporaneous they’re usually fragments of a larger body broken apart by the gravitational effect of the earth-Moon system.</p>
<p>A big asteroid strike dating back to over 300 million years left a huge impact zone in Australia, and changed the face of the earth forever, a new study has found.<br /><br /></p>.<p>The impact zone, which centres on the East Warburton Basin in north-eastern South Australia, was caused by an asteroid up to 20 kilometres-wide that slammed into the planet between 298 and 360 million years ago, researchers at Australian National University (ANU) and University of Queensland have claimed.<br /><br />Terrain around the impact site shows evidence of changes caused by shock-wave related deformation and heating of the ground by an impact event, Andrew Glikson of ANU was quoted as saying by Australian Broadcasting Corporation.<br /><br />“This shock metamorphic terrain covers an area of over 30,000 square kilometres making it the third-largest site of its kind ever discovered on earth,” Glikson said.<br />To confirm the area was an impact zone, Glikson and colleagues studied quartz grains retrieved from drill holes.<br /><br />Optical and electron microscopic examination revealed tiny fractures, which indicate the quartz grains had been shocked by an asteroid or meteor impact.<br /><br />“This is the only way these features are formed,” he said. Follow up observations detected deep seismic anomalies below the terrain where the samples were taken.<br />“This allowed us to determine the scale of the impact site which is buried under four kilometres of younger sediments,” Glikson said.<br /><br />He said that there is a link between this impact site and three or four other large impact sites of the same age scattered around Australia.<br /><br />“Asteroid impacts commonly occur in clusters of two or more projectiles,” he said, adding “Where impacts are near- contemporaneous they’re usually fragments of a larger body broken apart by the gravitational effect of the earth-Moon system.</p>