Introduction

The Hawaii-Emperor volcanic chain is iconic in that its sharp bend around 50 Ma led to the early proposal of a sudden rotation in the moving direction of the giant Pacific plate amidst a global plate reorganization. However, a later proposal based on paleomag stated that this bend marks merely the end of southward motion of the underlying plume that formed this chain. Since then, this debate has continued for over a decade by now because none of the proposed models could simultaneously explain all the data. Our recent paper, "The Role of Plume-Lithosphere Interaction in Hawaii-Emperor Chain Formation," published in Nature Communications, delves into the intricate dynamics that have shaped the Hawaii-Emperor chain. This study leverages advanced data-assimilation models to systematically explore an underexplored aspect, the interaction between the Hawaiian plume and the overlying lithosphere at upper-mantle depth, providing new insights into the formation and evolution of this volcanic chain.

The underestimated role of plume-lithosphere interaction

By testing different plate reconstruction models and multiple geodynamic scenarios, we arrived at a previously underestimated mechanism behind the hotspot chain: plume-lithosphere interaction. This interaction between the oceanic lithosphere and the mantle plume includes both plate drag and plume-ridge interaction, where the former always entrains the plume along the plate motion direction and the latter causes forward and backward plume migration as the ridge traverses the plume conduit.

Simulated Hawaiian plume evolution. 3D red contours represent the +100°C temperature anomaly. The 1% melt fraction is shown in white. The core-mantle boundary is shown in light blue, and plate boundaries are green lines. The top right corner of each snapshot shows the temperature contour (black) and melt area (red) of the plume, with their profile denoted by a black dotted line on top of the plume.

These processes strongly influence the melt formation and advection within the asthenosphere, causing the seemingly erratic changes in the seamounts’ paleomagnetic properties along the Hawaii-Emperor chain. This interaction accounts for approximately 50% of the observed variations in paleolatitude and the spatial-temporal distribution of the seamounts. Consequently, the amount of required southward plume migration, as previously proposed, is significantly less. This finding challenges existing hypotheses and suggests a more complex interplay of shallow and deep mantle processes.

Broader implications on hotspot chain dynamics

While this study focuses on one specific hotspot, its implications clearly extend beyond the Hawaii-Emperor chain. The identified plume-lithosphere interaction represents a common mechanism that could affect hotspot tracks globally. A brief analysis of multiple other hotspot chains confirms this. Therefore, the dynamic effects of moving plates on shallow mantle upwellings represent a widely underappreciated mechanism that is crucial for further understanding mantle dynamics and plate reconstructions.

Paleolatitude predictions and plume source motion. a) Blue dots with error bars represent observed paleolatitude of seamounts. Purple points are paleolatitudes estimated by correcting plate motion effects from the present Hawaii chain. The red line is the paleolatitude assuming no lateral plume motion at shallow depth, while the green line considers this motion. The northward velocity of the Pacific Plate is shown in the cyan dashed line. The gray dashed line is the latitude of the plume source trajectory with lateral migration of its shallow portion. b) The inferred lateral trajectory of the plume root at ~600 km depth.

Moving forward, we expect further research to refine these models and explore additional factors that could influence plume behavior and hotspot formation. This includes more detailed studies on the role of plume buoyancy and the mantle viscosity, as well as the lower mantle origin of the inferred plume kinematics. To achieve these goals, more comprehensive paleolatitude measurements and geochemical analyses of seamounts are likely needed. On the other hand, incorporating more sophisticated rheology and simulation within a global mantle domain may add more to the ultimate plume dynamics.

Overall, this study marks a major step forward in quantifying the various mechanisms pertinent to the formation of oceanic hotspot chains. By highlighting the critical role of plume-lithosphere interaction and challenging existing theories on plume migration, we hope to inspire future research that will continue to unravel the mysteries of Earth's dynamic interior. Carrying on the spirit of scientific communication and collaboration, we look forward to engaging with the community to discuss these findings and explore new avenues for research in mantle dynamics and plate tectonics.