The blocks may confirm volcano-triggered tsunami thousands of years ago

Sep 25, 2008 09:43 GMT  ·  By

The seven enormous coral chunks, as huge as a house, that have been cast away on Tonga's western shore may be linked to a giant volcano-triggered tsunami wave, claim scientists.  

On the remote island of Tongatapu, situated in the southern Pacific Ocean, researchers found evidence of an ancient natural catastrophe. Lying on the westernmost coast of the isle, there are seven huge coral boulders, similar in makeup to the coral reefs on the coast, which proves that they have been torn from their forming place and carried there.

  Some of the boulders are 30 feet (9,1 meter) high and as heavy as 3.5 million pounds (1.6 million kg). They seem to have been brought ashore several thousands of years back by a tsunami as big as the one caused by the eruption of the Krakatoa volcano in Indonesia 125 years ago. The wave that swept naked entire shores was about 130 feet (40 meters) high. In a recent statement, Matthew Hornbach from the University of Texas Institute for Geophysics said that "These could be the largest boulders displaced by a tsunami, worldwide."  

The scientist and his team are writing an ample report related to the coral boulders for next month's meeting of the Geological Society of America in Houston. They say that the chunks are so peculiar that the Tongan legends and folklore are abundant in tales on their origin. According to one of them, Māui, the demigod who had raised all the Hawaiian Islands from the bottom of the sea, hurled the boulders towards the shores in his attempts to slay a huge man-eating beast.  

"We think studying erratic boulders is one way of getting better statistics on mega-tsunamis," added Hornbach. "There are a lot of places that have similar underwater volcanoes and people haven't paid much attention to the threat."