“The other thing I’d started in a big way was looking at what had happened with mantle convection, the driving forces,” says McKenzie. “Plate tectonics works on the surface but clearly the Earth is not a rigid enterprise. So what went on below? It was clearly some form of thermal convectionthe transfer of heat by fluid flow as a consequence of pressure or temperature variations., but the rest of it was unknown.” McKenzie continued to work on the properties of the mantle, modelling the thermal structure with Jean RobertsJean M. Hewitt (birth name) / Jean M. Roberts (married name) (b. 1940-) graduated with a Physics degree from Manchester University. Taught physics at Cambridge Technical College (now Anglia Ruskin University). Gained software experience at the Cambridge Institute of Theoretical Physics in 1968 then joined Dan McKenzie and Nigel Weiss at Madingley Rise Bullard labs. in 1969 to create the mantle convection model. This was one of the first applications of (the then) significant computing resources required for modelling the Earth’s mantle (a Boussinesq fluid of infinite Prandl number). More complex models were developed and key papers written during the subsequent 11 years. In 1983 Jean joined the company Shape Data, (subsequently EDS, then Siemens) to develop the first boundary representation solid modeller Parasolid for CAD, (based on the PhD thesis of Ian C. Braid in the early 1970s), now the kernel of many modern computer research and design applications. She was appointed Secretary of the Institute of Biotechnology, University of Cambridge, in 1996, a post held for 12 years. and Nigel WeissNigel Weiss (1936-present) is a South African astronomer and mathematician specialising in astrophysical and geophysical fluid dynamics. He is currently Emeritus Professor of Mathematical Astrophysics at the University of Cambridge..