Atoll Evolution

High-resolution image (963 Kb)

In one photograph, International Space Station astronauts were able to capture the development and accumulation of coral reefs over geologic time scales from fringing reefs to atolls. Charles Darwin first developed this theory while visiting Tahiti using maps made by Captain Cook. In this image of the Leeward Islands of the Society Archipelago the islands are progressively older to the northwest. As these islands move away from their magma sources they erode and subside and the corals have gradually built the reef structure present today. The two large islands, Raiatea and Tahaa, share a single fringing reef. The next island to the northwest, Bora-Bora, consists of a highly eroded volcanic remnant with fringing reef. The last island, Tupai, signifies the destiny of these islands; the fringing reef has become an atoll with the central island below sea level.

The image was taken in February 2003 from the International Space Station using a digital camera as part of the Crew Earth Observations Project. Coral reefs are one of the areas selected as a scientific theme for this project.

Darwin's original book on coral reefs and their development is still used today and was reprinted in 1984. See The Structure and Distribution of Coral Reefs, University of Arizona Press, Tucson, Ariz.

Astronaut photograph ISS006-E-22132 is provided by the Earth Sciences and Image Analysis Laboratory at Johnson Space Center. The International Space Station Program supports the laboratory to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth.