Washington, Feb 4 (ANI): In a new research, scientists have determined that seven huge irregular boulders in an island in Tonga were deposited by a prehistoric mega tsunami thousands of years ago.

The research was done by Cliff Frohlich and her colleagues from the Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, in the US.

The hugely puzzling coral limestone boulders sit 100200 meters from the shoreline on the island of Tongatapu in the southwest Pacific.

In 2007, Frohlich studied these boulders, which have dimensions as large as 9 meters and weigh up to 1600 tons, and concluded that the boulders originated at the shoreline about 120,000 years ago and have since been displaced by a prehistoric tsunami.

Frohlich and her team analyzed undersea volcanic calderas in the Tofua arc west of Tongatapu and local slump features just offshore from the boulders and concluded that a caldera collapse was the likely cause of a tsunami large enough to move the boulders.

A systematic census and analysis of erratic boulders and other tsunamigenic features along shorelines elsewhere in the world may provide a means for extending the historic record and thus more accurately assessing tsunami hazard. (ANI)