Understanding the deep mantle structure and dynamics is one of the main challenges in the Earth interior sciences. The structure and dynamics of the Earth’s lowermost mantle are of particular interest. They play a critical role in Earth’s thermal evolution by controlling the core-mantle boundary heat flux. They dictate the formation of mantle plumes, which are responsible for the large igneous provinces and hotspots observed on the Earth’s surface. The compositional heterogeneities in the lowermost mantle provide important information for the Earth’s compositional evolution.

The Earth's lowermost mantle is characterized by two large low shear velocity provinces (LLSVPs). The regions outside the LLSVPs have generally higher seismic velocities than the LLSVPs and are often suggested to be strongly influenced by relatively cold subducted slabs. In addition to the large-scale structures, seismic observations have revealed wide-spread small-scale structures within and outside the LLSVPs. In this talk, I will present the results of our geodynamic modeling experiments that help to understand the origin and dynamics of the multi-scale structures in the lowermost mantle.