Natural Hazards

, Volume 63, Issue 1, pp 119–131 | Cite as

Inland fields of dispersed cobbles and boulders as evidence for a tsunami on Anegada, British Virgin Islands

  • Steve Watt
  • Mark Buckley
  • Bruce Jaffe
Original Paper


Marine overwash from the north a few centuries ago transported hundreds of angular cobbles and boulders tens to hundreds of meters southward from limestone outcrops in the interior of Anegada, 140 km east–northeast of Puerto Rico. We examined two of several cobble and boulder fields as part of an effort to interpret whether the overwash resulted from a tsunami or a storm in a location where both events are known to occur. One of the cobble and boulder field extends 200 m southward from limestone outcrops that are 300 m inland from the island’s north shore. The other field extends 100 m southward from a limestone knoll located 800 m from the nearest shore. In the two fields, we measured the size, orientation, and spatial distribution of a total of 161 clasts and determined their stratigraphic positions with respect to an overwash sand and shell sheet deposit. In both fields, we found the spacing between clasts increased southward and that clast long-axis orientations are consistent with a transport trending north–south. Almost half the clasts are partially buried in a landward thinning and fining overwash sand and none were found embedded in the shelly mud of a pre-overwash marine pond. The two cobble and boulder fields resemble modern tsunami deposits in which dispersed clasts extend inland as a single layer. The fields contrast with coarse clast storm deposits that often form wedge-shaped shore-parallel ridges. These comparisons suggest that the overwash resulted from a tsunami and not from a storm.


Caribbean Tsunami Storm 



We would like to thank Cynthia Rolli (British Virgin Island Disaster Management Agency) for sharing high-resolution aerial photos of Anegada for our field work and in this manuscript. Critical reviews by Uri Ten Brink and Brian Atwater improved the manuscript. Funding was provided by the “Tsunami Hazards Potential in the Caribbean” project of the U.S. Geological Survey and Marine Geology Program.

Supplementary material

11069_2011_9848_MOESM1_ESM.pdf (65 kb)
Supplementary material 1 (PDF 65 kb)


  1. Atwater BF, ten Brink US, Buckley M, Halley RS, Jaffe BE, Lopez-Venagas AM, Reinhardt EG, Tuttle MP, Watt S, Wei Y (2010) Geomorphic and stratigraphic evidence for an unusual tsunami or storm a few centuries ago at Anegada, British Virgin Islands. Nat Hazards. doi: 10.1007/s11069-010-9622-6
  2. Buckley ML, Wei Y, Jaffe BE, Watt SG (2011) Inverse modeling of velocities and inferred cause of overwash that emplaced inland fields of boulders at Anegada, British Virgin Islands. Nat Hazards. doi: 10.1007/s11069-011-9725-8
  3. Collinson JD, Thompson DB (1982) Sedimentary structures. George Allen and Unwin, London. p 194Google Scholar
  4. Di Geronimo I, Choowong M, Phantuwongraj S (2009) Geomorphology and superficial bottom sediments of Khao Lak coastal area (SW Thailand). Pol J Environ Stud. 18(1):111–121Google Scholar
  5. Dunn GE (1961) The hurricane season of 1960. Mon Weather Rev 89:99–108Google Scholar
  6. Etienne S, Paris R (2010) Boulder accumulations related to storms on the south coast of the Reykjanes Peninsula (Iceland). Geomorphology 114:55–70CrossRefGoogle Scholar
  7. Goff J, Dudley WC, deMaintenon MJ, Cain G, Coney JP (2006) The largest local tsunami in 20th century Hawaii. Mar Geol 226:65–79CrossRefGoogle Scholar
  8. Goto K, Chavanich SA, Imamura F, Kunthasap P, Matsui T, Minoura K, Sugawara D, Yanagisawa H (2007) Distribution, origin, and transport process of boulders deposited by the 2004 Indian Ocean tsunami at Pakarang Cape, Thailand. Sediment Geol 202:821–837CrossRefGoogle Scholar
  9. Inman DL (1949) Sorting of sediments in the light of fluid mechanics. J Sed Petrol 19:51–70Google Scholar
  10. Morton RA, Richmond BM, Jaffe BE, Gelfenbaum G (2008) Coarse-clast ridge complexes of the Caribbean: a preliminary basis for distinguishing tsunami and storm-wave origins. J Sed Res 78(9):624–637Google Scholar
  11. O’Loughlin KF, Lander JF (2003) Caribbean tsunamis: a 500 year history from 1948–1998. Kluwer Academic, DordrechtGoogle Scholar
  12. Paris R, Wassmer P, Sartohadi J, Lavigne F, Barthomeuf B, Desgages É, Grancher D, Baumert Ph, Vautier F, Brunstein D, Ch Gomez (2009) Tsunamis as geomorphic crisis: lessons from the December 26, 2004 tsunami in Lhok Nga, west Banda Aceh (Sumatra, Indonesia). Geomorphology 104(1–2):59–72CrossRefGoogle Scholar
  13. Pilarczyk JE, Reinhardt EG (2010) Homotrema rubrum (Lamark) taphonomy as an overwash indicator in marine ponds from Anegada, British Virgin Islands. Nat Hazards. doi: 10.1007/s11069-010-9706-3
  14. Reid HF, Taber S (1920) The Virgin Islands earthquakes of 1867–1868. Bull Seismol Soc Am 10:9–20Google Scholar
  15. Reinhardt EG, Pilarczyk JE, Brown A (2011) Probable tsunami origin for a shell and sand sheet from marine ponds on Anegada, British Virgin Islands. Nat Hazards. doi: 10.100/s11069-011-9730-y
  16. Richmond BM, Watt SG, Buckley ML, Jaffe BE, Gelfenbaum G, Morton RA (2011) Recent storm and tsunami coarse-clast deposit characteristics, southeast Hawai’i. Mar Geol 283(1–4):79–89Google Scholar
  17. Scheffers A (2005) Coastal response to extreme wave events-hurricanes and tsunami on Bonaire. Essener Geographische Arbeiten 37:100Google Scholar
  18. Scoffin TP (1993) The geological effects of hurricanes on coral reefs and the interpretation of storm deposits. Coral Reefs 12:203–221Google Scholar
  19. Wei Y, ten Brink US, Atwater BF (2010) Modeling of tsunamis and hurricanes as causes of the catastrophic overwash of Anegada, British Virgin Islands, between 1650 and 1800: Abstract OS42B-03 presented at 2010 fall meeting, American Geophysical Union, San Francisco,13–17 Dec 2010Google Scholar
  20. Williams DM, Hall AM (2004) Cliff-top megaclast deposits of Ireland, a record of extreme waves in the North Atlantic—storms or tsunamis? Mar Geol 206:101–117Google Scholar
  21. Zahibo N (2003) The 1867 Virgin Island Tsunami; observations and modeling. Oceanol Acta 26:609–621Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  1. 1.U.S. Geological SurveySanta CruzUSA

Personalised recommendations