One of the major motivations for the development of Sea Colonies was the discovery of vast untapped mineral resources lying just beneath the surface of the deep ocean floor. However, the greatest treasure lies much deeper, out of reach of machines built for mining from the Earth's crust. Only the discovery Matter Distortion allowed for economically viable, mass-scale excavation of minerals from the mantle deposites. Such mines could only be built on the ocean floor though, where the crust was much thinner than on the continental plates.