Geological effects of tsunami on mid-ocean atoll islands: The Maldives before and after the Sumatran tsunami
- Paul S. Kench*1,
- Roger F. McLean2,
- Robert W. Brander3,
- Scott L. Nichol4,
- Scott G. Smithers5,
- Murray R. Ford6,
- Kevin E. Parnell7 and
- Mohamed Aslam8
- 1School of Geography and Environmental Science, University of Auckland, Private Bag 92019, Auckland, New Zealand
- 2School of Physical, Environmental and Mathematical Sciences, University of New South Wales,Canberra ACT 2600, Australia
- 3School of Biological Earth and Environmental Science, University of New South Wales, Sydney, NSW 2052, Australia
- 4School of Geography and Environmental Science, University of Auckland, Private Bag 92019, Auckland, New Zealand
- 5School of Tropical Environment Studies and Geography, James Cook University, Townsville, QLD 4811, Australia
- 6School of Geography and Environmental Science, University of Auckland, Private Bag 92019, Auckland, New Zealand
- 7School of Tropical Environment Studies and Geography, James Cook University, Townsville, QLD 4811, Australia
- 8Ministry of Environment and Construction, Male, Republic of Maldives
Abstract
Low-lying coral islands are fragile landforms susceptible to long-term sea-level rise and extreme events, such as hurricanes and tsunamis. The Sumatran earthquake of 26 December 2004 generated waves that reached the Maldives 2500 km away. Observations of the effects of the tsunami are presented here, based on pre- and post-tsunami topographic and planform surveys of 13 uninhabited Maldivian islands. The surveys showed there was no substantial island erosion and no significant reduction in island area. Rather, the tsunami accentuated predictable seasonal oscillations in shoreline change, including localized retreat of exposed island scarps by up to 6 m, deposition of cuspate spits to leeward, and vertical island building through overwash deposition of sand sheets up to 0.3 m thick, covering up to 17% of island area. These results have implications for island stability indicating that low-lying reef islands are physically robust and the geological signature of tsunamis on atoll island development is minor.
Footnotes
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↵*p.kench{at}auckland.ac.nz
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↵GSA Data Repository item 2006033, methods; Figure DR1, location and planform characteristics of study islands; Figure DR2, summary of the physical impacts of tsunami on 12 islands; Table DR1, physical characteristics of study islands and reefs; and Table DR2, island area characteristics for pre-and post-tsunami surveys, are available online at www.geosociety.org/pubs/ft2006.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301-9140, USA.
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- Accepted 16 November 2005.
- Received 30 May 2005.
- Revision received 5 October 2005.
- Geological Society of America
