Tracking variations in volcano construction and lithospheric flexure along the Hawaiian-Emperor Seamount Chain

The Hawaiian-Emperor seamount chain is one the most prominent examples of a volcanic chain on the surface of the Earth, and has long been considered a hotspot track generated by the motion of the Pacific plate over a deep mantle plume. As individual volcanoes of the chain grow, they apply a downward load on the seafloor and progressively deform the lithosphere. The resulting flexure is manifest in the deep bathymetric depression that flanks the volcanic chain. A key aspect that impacts plate loading and rheological models of the lithosphere is the distribution of material added to the crust by magmatic activity. Previous studies suggested a range of possibilities, from volcanic construction being confined to the region above the oceanic crust, to some new material added within the crust, to some material “underplated” to the bottom of the crust. To investigate these and other issues, a set of marine geophysical field studies were carried out across the Emperor and Hawaiian Ridges. Seismic images from three lines that cross the volcanic chain reveal the amount of new material added to the plate, the internal structure of the volcanoes and underlying lithosphere, the thickness of erosional material in the surrounding moats, and the shape and degree of flexure of the lithosphere. The data allow us to compare plate loading and flexure for a load emplaced at a time when the plate was relatively young (Emperor Ridge) to a time when the plate was relatively old (the Hawaiian Ridge) and will lead to better age-dependent loading and response models for oceanic lithosphere.