Scientists from Australia, New Zealand and the United States have come up with evidence of massive objects having struck the Earth's oceans thousands of years ago, causing tsunamis that dwarf the ones experienced in recent times.
There have been up to 10 such impacts in the past 10,000 years, claimed Australian geomorphologist Ted Bryant of the University of Wollongong, Assistant Professor Dallas Abbott from the Lamont-Doherty Earth Observatory at Columbia University and New Zealand-based tsunami expert Dr Mauri McSaveney of GNS Science.
Bryant was quoted by ABC Online as saying that the mega-tsunamis of yore were at least 10 times bigger than the December 26,2004 Asian tsunami.
"Aceh (in Indonesia) was a dimple compared to what we're looking at," says Bryant, who used satellite images from Google Earth to identify inland dunes in the shape of arrowheads that he says are signs of the mega-tsunamis.
The tsunamis would have displaced marine deposits containing marine fossils, he says, dumping them inland as 'chevron' dunes.
"We've found that chevrons are everywhere, everywhere around the world's coasts," he says.
Abbot used sea surface altimetry, which measures the height of the sea surface to get an image of the seabed, to identify possible underwater craters, which could be evidence of the impact that caused the tsunamis.
Bryant says Abbot also looked for melted material in cores from the seabed around the craters to confirm impacts caused them.
Bryant says chevrons about 4800 years old around the Indian Ocean are associated with a 29-kilometre wide impact crater located thousands of kilometres to the southeast of Madagascar.
Bryant says other evidence of a mega-tsunami as recently as 500 years ago has been found on the eastern coast of Australia.
None of the research has been published but some of it will be presented at an American Geophysical Union meeting in San Francisco next month
However, Earth scientist Professor Richard Arculus of the Australian National University and marine sediment specialist Dr Bradley Opdyke believe that more evidence is required to corroborate this view.
They, however, accept that Bryant's claims are "perfectly plausible", but need substantiation. (ANI)