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Science 14 September 1973:
Vol. 181. no. 4104, pp. 1040 - 1042
DOI: 10.1126/science.181.4104.1040
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Articles

Gravitational Evidence for a Low-Density Mass beneath the Galápagos Islands

J. E. Case 1, S. L. Ryland 2, Tom Simkin 3, and K. A. Howard 4

1 U.S. Geological Survey, P.O. Box 6732, Corpus Christi, Texas 78411
2 California Institute of Technology, Pasadena 91109
3 Smithsonian Institution, Washington, D.C. 20560
4 U.S. Geological Survey, Menlo Park, California 94025

A residual negative free-air and Bouguer anomaly of at least 80 milligals, superimposed on a broader high, occurs over the Galápagos Islands The axis of the anomaly trends roughly east and plunges eastward. Thus, a low-density mass in the crust or upper mantle must underlie the archipelago. This anomaly may be caused by thermal expansion over a crust-mantle " hot spot".

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Science. ISSN 0036-8075 (print), 1095-9203 (online)