The Committee on Mathematical Geophysics is an Inter-Association Committee of the IUGG. It aims to encourage exchange of ideas and information in all areas of geophysics, with emphasis on the application of mathematics, statistics and computer science to geophysical problems. The Committee organizes bi-yearly conferences.

During the report period I participated in the 22nd International Conference on Mathematical Geophysics, held in Cambridge UK on July 12-17, 1998 at the Isaac Newton Institute. The conference, titled "The Dynamic Earth", was well organized by the LOC under Herbert Huppert. Forty people attended the five day conference, comprising eight symposia and two poster sessions.

The scientific level of the conference and the quality of the presentations was high to very high, offering the tintillating experience of being among "real scientists". The symposia were titled:

- Geophysical Inverse Theory and Image Reconstruction

- Atmospheric Dynamics and Secular Variation

- Small Scale Processes in the Mantle

- Large Scale Mantle Convection

- Ocean Circulation, Global Climate, Heat Transfer and Turbulence

- Modern Numerical Investigations

- Magnetic Field Generation and Core Dynamics

- Crustal Processes: Deformation, Friction and Rupture

As seen from the symposium titles, the work reported focuses on understanding the behaviour of all the concentric "onion shells" that make up our dynamic Earth, and we are starting to see a lot of detail already. I feel this complex of issues to be relevant for geodesy in four ways:

- The mass distribution inside the Earth, affected by convection and plate tectonics, imprints itself on gravity field and geoid as studied by physical geodesy.

- Crustal motions, due to plate tectonics and other processes inside the Earth, are relevant to GPS geodesy.

- The atmosphere, especially "wet" troposphere and ionosphere, are well observable with the geodetic GPS infrastructures now existing in many countries. To fully use this, an understanding of atmospheric processes is essential.