Giant Tsunami Washed Ashore 600 Years Ago

Oct. 29, 2008 -- A massive Indian Ocean tsunami, similar in size to the behemoth that claimed a quarter of a million lives in December 2004, smashed into Thailand and Indonesia around 600 years ago, scientists believe.

The evidence comes from deposits of sand washed inland by colossal waves and preserved under layers of coastal peat, according to studies published in Thursday's issue of Nature, the London-based science journal.

The December 2004 tsunami was triggered by an earthquake of 9.2 magnitude that ripped open the Sunda Trench -- the fault that zigzags up the eastern side of the Indian Ocean -- along 1,500 kilometers (950 miles).

Around 220,000 people were killed in a dozen countries.

The two teams pored over coastal areas in Indonesia and Thailand, seeking sheets of sand that had been deposited in past tsunamis but had been left undisturbed by wind, rivers, storms, animals or humans.

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They found the sedimentary treasure by drilling core samples in "swales," or dips between beach ridges, that are filled with peaty marsh.

The Indonesian site was found around two kilometers (1.2 miles) inland north of the town of Meulaboh in Aceh province, on Sumatra's northern tip, where waves up to 35 meters (113 feet) above sea level were recorded in 2004.

The Thai location was at Phra Thong Island, 124 kilometers (77 miles) north of the resort of Phuket, where the 2004 tsunami reached heights of up to 20 meters (65 feet).