"A mega-tsunami rivaling the deadly one in 2004 struck southeast Asia
more than 600 years ago, two teams of geologists said after finding
sedimentary evidence in coastal marshes.
Researchers in Thailand and Indonesia wrote in two articles in the
journal Nature that the tsunami hit around 1300 or 1400, long before
records of earthquakes in the region began to be kept.
"Tsunamis are something we never experienced before, and after 2004
people thought it was something we would never experience again,"
Kruawun Jankaew of Chulalongkorn University in Thailand said in a
"But from this, we are able to identify that the place has been hit by
a mega-tsunami in the past," she said. "So even though it is
infrequent for this part of the world, it still happens and there is a
need to promote tsunami education for coastal peoples."
The tsunami in 2004 left 230,000 people either dead or missing across
Asia, from Sri Lanka and India to Thailand, the Maldives and
Indonesia. More than 170,000 victims were in Aceh Province in
Ms. Jankaew's team studied a grassy plain on Phra Thong, an island
north of Phuket in Thailand, where the 2004 tsunami reached wave
heights of 65 feet above sea level.
A separate team led by Katrin Monecke from the University of
Pittsburgh looked at sedimentary records on coastal marshes in Aceh,
where the waves reached 115 feet.
They explored low areas between beach ridges called swales, which are
known to trap tsunami sand between layers of peat and other organic
matter, and discovered a layer of sand beneath the most recent layer,
from 2004, that was from an event that occurred 600 to 700 years ago.
Scientists are trying to determine the scale of the tsunami that
happened long ago. "We will look at the thickness and grain size of
the sediment and we can calculate how fast the tsunami was, how far
inland it went and the floor depth," Ms. Jankaew said."
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