Geomagnetic evidence for a continuously connected plume conduit extending to at least the 660-km discontinuity below Hawaii

Do plumes exist? If so, do plume tails connect hotspots to the core-mantle boundary (CMB), or only to the 660-km discontinuity (between the upper and the lower mantle)? Are they continuous or fragmented? Here, we demonstrate quantitatively that the Hawaiian plume distorts 24-h-period magnetovariational data by providing a continuous electrical connection between the Earth's surface (via the ocean) and the 660-km mid-mantle discontinuity. We extend our analysis to predict how a plume ascending from the CMB should distort magnetic secular variation observed locally at the surface. Hence, the Hawaiian plume is demonstrated to be a continuous feature with a deep-seated (at least mid-mantle) source. Our analysis provides a novel technique for determining whether the Hawaiian plume originates at the mid-mantle transition zone or CMB subject to magnetic secular variation data being acquired locally, as well as allowing the depth of genesis of other mantle plumes to be constrained should further geomagnetic data become available in their vicinity.