ISLANDS
Volcanic Islands and Atolls
Among his many contributions to our understanding of the natural world, Charles Darwin
hypothesized on the formation of atolls across the Pacific Ocean. For this exercise, you will have
an opportunity to experience observations like those made by Darwin during his time aboard
HMS Beagle.
Fig. 1.
Google Earth image of Bikini Atoll, Republic of the Marshall Islands
Based on his observations of Pacific island archipelagos during his cruise on HMS Beagle in the
first half of the 1800, Darwin hypothesized that atolls represented the final stage in the cycle of
volcanic islands. For this assignment, you should attempt to locate a series of images from
various places across the Pacific Ocean to illustrate Darwin’s Atoll Hypothesis—Darwin’s idea
was confirmed by the Royal Society Coral Reef Expedition of 1896-1898, during which the
island of Funafuti was drilled to reveal coral overlying volcanic rocks.
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Fig. 2.
Darwin’s hypothesis for atoll formation (From “Structure and Distribution of Coral Reefs”, 1842).
1. To begin the assignment, start Google Earth and go to the Pacific Ocean.
2. Search the images of Pacific islands until you find a compete series showing a) high volcanic
island with little or no reef development, b) high volcanic island with fringing reefs, c)
eroded volcanic island with barrier reef and developing lagoon, d) atoll.
3. Save each image you find and print them to turn in to your instructor.
LINKS TO RELATED SITES:
Wikipedia entry on Atolls: http://en.wikipedia.org/wiki/Atoll
Darwin’s “Voyage of the Beagle”: http://www.esp.org/books/darwin/beagle/
Darwin’s “Structure & Distribution of Coral Reefs”:
http://pages.britishlibrary.net/charles.darwin4/coral/coral_fm.html
Darwin the Geologist: http://gsahist.org/gsat/gt96dec8_10.pdf
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