How should the seismic irregularities observed in the lowermost 100–200 km of the mantle (the D″ layer) be partitioned between thermal and chemical heterogeneity, anisotropy, and core-mantle boundary (CMB) topography? How smooth is the core-mantle boundary? Do mantle convection and the thickness of D″ regulate the core geodynamo? How large is the outward temperature fall across the D″ layer? What is the temperature within the core? At what depths, or range of depths, do the vigorous upwellings and downwellings, demanded by dynamo action, occur within the outer core? Are seismically excited internal oscillations of the outer core observationally detectable in surface superconducting gravimeter records?
These constitute an illustrative sample of the questions discussed by almost 200 scientists at the first Study of the Earth's Deep Interior (SEDI) symposium entitled “Structure and Dynamics of the Core and Adjacent Mantle,” held on the Costa Brava of Spain, at Blanes from June 23–25, 1988, in conjunction with the 17th International Conference of the Committee on Mathematical Geophysics. SEDI is a new committee of the International Union of Geodesy and Geophysics, created at the Vancouver General Assembly in August 1987. This symposium and the SEDI secretariat have been sponsored by the National Science Foundation with help from the National Aeronautics and Space Administration. The following is a report of the SEDI symposium, which consisted of 13 oral presentations, 48 posters, and 5 open discussion periods during which the posters and general issues were discussed.