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The Indian Ocean gravity low - Evidence for an isostatically uncompensated depression in the upper mantleThe broad gravity low in the equatorial Indian Ocean south of Sri Lanka is the largest and most striking feature in the gravitational field of the earth. The most negative long-wavelength free-air gravity anomalies are found there and the sea surface (geoid) lies more than 100 meters below the best fitting ellipsoid. A model of the lithosphere and upper mantle is proposed which accurately predicts the observed free-air gravity and geoid elevation. This model is consistent with bathymetry and sediment thickness data and suggests that the crust south of India currently floats as much as 600 meters lower than would be expected if the region were isostatically compensated. This residual depression of the crust is apparently confirmed by observations of ocean depth. An uncompensated depression is consistent with the presence of a mechanical wake left in the upper mantle behind India as it traveled toward Asia.
Document ID
Document Type
Reprint (Version printed in journal)
Ihnen, S. M. (Colorado Univ. Boulder, CO, United States)
Whitcomb, J. H. (Cooperative Institute for Research in Environmental Sciences Boulder, CO, United States)
Date Acquired
August 11, 2013
Publication Date
June 1, 1983
Publication Information
Publication: Geophysical Research Letters
Volume: 10
ISSN: 0094-8276
Subject Category
Funding Number(s)
CONTRACT_GRANT: USGS-14-08-0001-20556
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