Geology

The Hazards of Overbuilding

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Science  16 May 2003:
Vol. 300, Issue 5622, pp. 1055-1057
DOI: 10.1126/science.300.5622.1055e

Many oceanic volcanic islands subside after they form (and eventually become atolls) or sink and become seamounts. Some volcanic islands are still undergoing uplift, and these have the potential to generate tsunamis as a result of landslides that occur when part of an overbuilt island becomes too steep and collapses. Ancient slides have been observed around Hawaii in the Pacific and the Canary Islands off Africa in the equatorial Atlantic. The future hazard posed by the Canary Islands has been uncertain because its current and past dynamics have been less clear than for the Hawaiian Islands. Hildenbrand et al. studied the morphology and uplift age of La Palma, the westernmost Canary island. Their observations of slope and valley morphology and their dating of uplifted lava flows and sediments imply that this island has been (and still is) rising at a surprisingly constant rate of about 0.5 mm/year during the past 4 million years.—BH

Earth Planet. Sci. Lett. 10.1016/S0012-821X(03)00133-X (2003).

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