Greenland Ice Sheet stratigraphy. Computer graphic showing the stratigraphy data collected by a radar aircraft flight over the Greenland Ice Sheet. This is a mass of ice with an area of 1.7 million square kilometres, reaching a thickness of over 3 kilometres. The resulting visualisation is known as a radargram. The shadow of the aircraft is at top right. This data was collected by one of the flights that form part of NASA's Operation IceBridge (2009-2016). This flight took place on 2 May 2011. The oldest ice, across bottom near the bedrock, is over 90,000 years old. For the lines colour-coded and with age labels, see image C025/8969.