Our understanding of the earth's dynamics has chiefly been obtained through long-term geophysical observations on land. This limits and possibly biases our understanding of how continents grow or how ocean floors recycle in the mantle. To improve our understanding of these questions, we require higher resolution and more accurate data on the 3-D internal structure and dynamics of the earth. To do this we must conquer the ocean floor, the last frontier of intra-earth exploration. Initiatives are now being made in this direction.
Observational gaps exist in space, in time, in frequency, and in dynamic range.
The fates of plates in the mantle, their role in mixing the mantle and possibly causing plumes, and observations that can improve our understanding of these phenomena were the main theme. This special issue of EPS is an outcome of the symposium, and consists of 16 solicited papers. The next five papers discuss the detailed three dimensional seismic structure beneath the East Asia-West Pacific region where the OHP network will be deployed. They are followed by two seismology papers on the global scale problems. And the final five papers are on the geodynamical inferences and consequences of the geophysical observations on the different parts of the mantle.