A Synoptic View of Mantle Plume Shapes Enabled by Virtual Reality

The shapes of mantle plumes are sensitive to mantle viscosity, density structure, and flow patterns. Increasingly, global tomographic models reveal broad plume conduits in the lower mantle and highly tilting conduits in the mid and upper mantle. Previous studies mostly relied on 2D slices to analyze plume shapes, but fully investigating the complexity of 3D plume structures requires more effective visualization methods. Here, we use immersive headset-based virtual reality (VR) to visualize the full-waveform global tomographic models SEMUCB-WM1 and GLAD-M25. We develop criteria for the identification of plume conduits based on the relationship between the plume excess temperature and the VS anomaly (delta VS). We trace 20 major plume conduits, measure the offsets of the conduits in azimuth and distance with respect to the hotspots, calculate the tilt angle, and evaluate the delta VS along all traced conduits. We compare our traced conduits with the conduits predicted by global mantle convection models and vertical conduits. The wavespeed variations along conduits traced from each tomographic model are slower than modeled or vertical conduits, regardless of which tomographic model they are evaluated in. The shapes of traced conduits tend to differ greatly from modeled conduits. Plume ponding and the emergence of secondary plumes, which could result from a combination of compositional variations, phase transitions, small-scale convection, and variations in viscosity, can contribute to the complex observed plume shapes. The variation of delta VS along the traced conduits and complex plume shapes suggest a thermochemical origin of many plumes. The variation of shear velocity anomaly along the traced conduits and complex plume shapes suggest a thermochemical origin of many plumes We identify complex plume shapes (ponding, branching, and merging) that suggest a complex rheological structure of the lower mantle We provide systematic and quantitative observations of plume shapes that can benefit numerical modeling and geochemical studies of plumes