Remote sensing of the Earth’s interior using seismic waves and other geophysical observations reveals a complex, three-dimensional structure. This structure is thought to be a consequence of convective mass transport, driven by slow cooling of the planet from a hot initial state. Supporting evidence for internal complexity comes from geochemical analysis of melts that erupt on to the surface. Systematic variations in chemistry and isotopic composition are related to the physical structure, but the connection between the physical structure and the geochemical heterogeneity is a long-standing question that holds the key to documenting the geological history that brought the Earth to its current state. The purpose of CIDER 2018 is to bring together junior and senior scientists from different disciplines to cross-educate each other and help advance our understanding of the processes that govern the long-term evolution of our planet.