Special Seminar by Professor D. Dobson (UCL) on Thursday July 18.

Professor David Dobson from the University College of London will give a special seminar at the Geophysics section on July 18, entitled "Greater than the sum of the parts: grain boundaries under high pressure".

He will present an overview of observations which suggest that grain boundaries significantly reconstruct as a function of pressure such that their mechanical behaviour might be fundamentally different in the lower mantle and discuss recent measurements which show that this high-pressure reconstruction inhibits grain-boundary sliding even at sub-micron grain sizes.  This suggests that (1) extrinsic seismic attenuation might be important in the lower mantle and (2) a fine-grained (<100 micrometre) lower mantle would be consistent with all of the geophysical and experimental petrological constraints.