The December 26, 2004 Indian Ocean Tsunami: Initial Findings on Tsunami Sand Deposits, Damage, and Inundation in Sri Lanka
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Tsunami Sand DepositsThe tsunami in Sri Lanka carried sand from the beach and ocean floor and deposited it in buildings, on top of boulders, and on the ground. Tsunami sand deposits were found at all sites that the East and South Sri Lanka Teams visited. Although tsunamis are capable of eroding the land, erosion in Sri Lanka was often concentrated in a relatively narrow zone near the coast. For example, at Mankerni, there was evidence that a grassy area eroded about 1 meter in the vertical in a zone about 20 to 30 meters wide near the coast. The sand eroded was transported both onshore and offshore. The sand transported onshore formed a recognizable tsunami sand deposit. Tsunami sand deposits at Mankerni started about 50 meters inland, and decreased in thickness from about 10 centimeter total thickness to about 2 cm thickness at about 150 meters inland. In other locations where the tsunami was larger, both the width of the erosion zone and the tsunami deposit were larger. |
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Although the tsunami receded long before the ITST arrived in Sri Lanka, the sand that remained can tell us much about the tsunami. The tsunami sand deposits often contained two or more layers. These layers were formed by different tsunami waves and by variations in flow within a wave. Analysis of the sand samples collected will add information that the Sri Lanka ITST was not able to collect about the tsunami. For example, from lab analyses and computer modeling of the tsunami sand deposits, we will be able to estimate the speed (flow velocity) of the tsunami as it moved inland.
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last modified 2005