VARIATION OF THE APPARENT COMPENSATION DEPTH OF HOTSPOT SWELLS WITH AGE OF PLATE

Abstract

Most oceanic hotspot swells are associated with anomalously shallow seafloor and broad geoid anomalies. These depth and geoid anomalies are generally positively correlated and linearly related. The linear relationship can be used to infer an apparent depth of isostatic compensation of the swell. We have analysed geoid and depth anomalies over 23 oceanic hotspot swells (almost the majority of oceanic hotspots) and deduced the apparent depth of compensations of these features. The data indicate a linear increase of the compensation depth with the square root of seafloor age t, on the order of 7 km/(m.y.)1/2. This trend is comparable to that predicted by conductive cooling models for the deepening of the isotherms inside the oceanic lithosphere.