Gravity and topography near Hawaii

The narrow volcanic ridge loads the lithosphere and generates a regional flexural response, while the broad swell involves deeper support. The observed positive ridge anomaly, negative flanks, outer positive belt, and long-wavelength positive swell anomaly probe distinct spatial scales.^[ref]

The Hawaiian swell is the broad elevation of the seafloor on which the narrower Hawaiian volcanic ridge sits. These are different spatial scales: the volcanic load bends the lithosphere through lithospheric flexure, while the broad elevation requires an explanation for deeper or more distributed support.

Ship and submarine gravity measurements show a long-wavelength positive anomaly correlated with the swell, distinct from the larger local ridge and flanking anomalies. The original analysis found that ridge crustal structure alone was unlikely to explain the long-wavelength signal and discussed compensation associated with flow beneath the lithosphere.^[ref] Combining gravity-topography admittance with other observations helps test support models; topography alone does not uniquely identify a deep mass density distribution.