Scratch marks on the ocean floor off western Greenland mark the passing of the largest icebergs ever known to have existed. At more than 950 metres from top to bottom, these behemoths would dwarf anything we see today and make the 30-metre-high berg that sank the Titanic look like an ice cube. The scratch marks date back to the last ice age, more than 12,000 years ago.
The gouges were found in sonar images of the sea floor made by Antoon Kuijpers of the Geological Survey of Denmark and Greenland, in Copenhagen, and his colleagues. They measured the furrows to be around 750 m wide and 40 m deep (Marine Geology, DOI: 10.1016/j.margeo.2007.05.010). The sea above the furrows was 950 m at the deepest (around 120 m lower than today) when these icebergs scraped along the seabed, making them at least that tall. 鈥淭heir keel depths were about twice as much as the largest Antarctic icebergs of today,鈥� says Kuijpers.
Dating the scratch marks is difficult, but it is clear they were formed during the last ice age. Such icebergs are unlikely to reappear in the northern hemisphere any time soon, but if the planet warms fast enough we could see similar beasts surging forth from Antarctica, says Kuijpers.
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