Encyclopedia of Modern Coral Reefs

2011 Edition
| Editors: David Hopley

Coral Cay Classification and Evolution

  • Scott G. Smithers
  • David Hopley
Reference work entry
DOI: https://doi.org/10.1007/978-90-481-2639-2_6


A coral cay is an island formed from sediments derived from the reef on which it sits and swept by refracted waves to a focal point on the reef flat where they are deposited. A cay initially may remain intertidal and lack vegetation, but with time it is likely to build up to be above sea level, acquire a vegetation cover, and become partially lithified.


Islands associated with coral reefs have been occupied or used by humans for millennia. They became known to western society as voyages of discovery crossed tropical waters. A distinction has been made between “high” islands composed of continental rocks and “low” islands of biogenic carbonate sediments produced by reef organisms. The variety of morphologies that were observed became a focus of early studies:

“There are different opinions amongst ingenious theorists, concerning the formation of such low islands”.

(James Cook, 17 April, 1777)

Scientific studies of reef islands were first made in the nineteenth...
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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Scott G. Smithers
    • 1
  • David Hopley
    • 1
  1. 1.School of Earth and Environmental SciencesJames Cook UniversityTownsvilleAustralia