Authors: A.R. McBirney and Howel Williams
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More than sixty scientists took part in the Galapagos International Scientific Project conducted by the University of California Extension Division with the support of the National Science Foundation and the Charles Darwin Foundation. The authors were part of the geologic contingent of that expedition. The Galapagos Archipelago constitutes one of the world's largest and most active groups of oceanic volcanoes. Chemically the rocks differ from those of Hawaii; they are probably typical of igneous rocks related to the East Pacific Rise. Plutonic and effusive tholeiitic rocks follow parallel courses of differentiation with enrichment in Fe/Mg, total alkalis, and excess silica. Alkali basalts are derived from a deeper source than are the tholeiitic rocks and show little evidence of differentiation. The islands were never connected to the main land of South or Central America. They grew from a broad shallow platform near the crest of the East Pacific Rise, and the location of individual volcanoes appears to have been controlled by two major fracture systems, one trending north-northwest and the other nearly east-west.
Published: 9/01/1969
ISBN Number: 0-8137-1118-5
Pages: 197
Product Category: Memoirs