Thermal origin of the Hawaiian swell: Heat flow evidence and thermal models

Abstract

The lithospheric reheating hypothesis for the origin of the Hawaiian swell has been tested by heat flow measurements along the swell between Hawaii and Midway. Ninety five measurements at eight carefully selected sites show that the heat flux on the swell increases systematically from near‐normal values (52±2 mW m−2) near Hawaii to values near Midway (59±2 mW m−2) about 20–25% higher than normal for lithosphere of that age (110 m.y.). This heat flow pattern is qualitatively consistent with a deep‐seated thermal anomaly created in a lithospheric plate moving across a fixed heat source. Modeling of the heat flow and bathymetry data on the Hawaiian swell strongly suggest that the swell is caused by a rapid heating (within <5 m.y.) of the lower part (>40‐ to 50‐km depth) of normal 90‐m.y.‐ old lithosphere over a relatively broad (500–1000 km) region near Hawaii. This model is also consistent With gravity and geoid anomalies associated with the swell, which require a low‐density region in the lower lithosphere, and with flexure studies of seamounts in the Hawaiian chain, which indicate that the rigidity of the lithosphere is not significantly reduced by the reheating.Appendices A‐C are available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document J82‐005; $1.00. Payment must accompany order.