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Ten craters found in the Pampas near Rio Cuarto in Argentina which were thought to have formed around 10,000 years ago may not be impact craters at all reports National Geographic. The Rio Cuarto craters were discovered in 1991 and the largest is 4.5 km across. Because of their alignment and elongated shapes the craters were thought to have been formed by a single asteroid which collided with the Earth's surface at a low angle and broke-up into pieces. New research by Dr Phil Bland from the Open University, however, suggests that these depressions in the Pampas were probably not formed by an impact despite the presence of impact glass and fragments of meteorites. Dr Bland discovered over 100 new elongated depressions in the Rio Cuarto area in satellite images and therefore suspected that the 'craters' might have an alternative explanation. Field work in the area, conducted by Bland, resulted in the discovery of more meteorites but of many different types suggesting these have accumulated with time rather than being samples of an impactor. The depressions, therefore, Bland suggests, are deflation basins caused by wind erosion rather than a collision since they line up with the prevailing wind direction. Impact glass, found in many of the depressions, however, did form in a collision somewhere in the Pampas, says Bland, and it is found in the depressions because it is here that it is exposed at the surface. This new interpretation of the Rio Cuarto craters illustrates that craters, in particular small craters, are very difficult to recognise on the Earth's active surface.
More info: National Geographic
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