A hypothesis which was strongly supported by Warren Carey (1911–2002), but which was first proposed by M. R. Mantovani in 1907, and raised again in the 1930s by Hilgenbirg and others. It holds that the diameter of the Earth has increased with time, fragmenting the continents and causing the growth of ocean basins at spreading axes (ridges). A conference to discuss the idea was hosted by Carey at Hobart, Tasmania, in 1956.