Geologic Evidence for Indian Ocean Tsunamis
Kruawun Jankaew led a team of geologists who unearthed evidence that tsunamis have repeatedly washed over a Thai island during the last 2,800 years.
Source: Brian Atwater
Ever since I read Simon Winchester’s Krakatoa, I’ve been fascinated with tsunamis and their ridiculous destructive power. The tsunamis generated by the explosion of Krakatoa in 1883 were upwards of 40 meters in height. The destruction that such a tsunami could cause was unimaginable.
Then the Indian Ocean earthquake in 2004 happened and the resulting tsunami was equally as destructive.
2004 Indian Ocean tsunami
Recently, a team from the University of Washington was working on the Phra Thong barrier island in Thailand has uncovered evidence of three previous major tsunamis that occurred in the region over the past 2,800 years.
The team found evidence for previous tsunamis by digging pits and auguring holes at more than 150 sites on an island about 75 miles north of Phuket, a Thai tourist resort area ravaged by the 2004 tsunami. That tsunami was generated 300 miles to the west when the seafloor was warped during a magnitude 9.2 earthquake.
At 20 sites in marshes, the researchers found layers of white sand about 4 inches thick alternating with layers of black peaty soil. Witnesses confirmed that the top sand layer, just below the surface, was laid down by the 2004 tsunami, which ran 20 to 30 feet deep across much of the island.
Radiocarbon dating of bark fragments in soil below the second sand layer led the scientists to estimate that the most recent predecessor to the 2004 tsunami probably occurred between A.D. 1300 and 1450. They also noted signs of two earlier tsunamis during the last 2,500 to 2,800 years.
There are no known written records describing an Indian Ocean tsunami between A.D. 1300 and 1450, including the accounts of noted Islamic traveler Ibn Battuta and records of the great Ming Dynasty armadas of China, both of which visited the area at different times during that period. Atwater hopes the new geologic evidence might prompt historians to check other Asian documents from that era.
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