Nicolas Coltice

A hologram is an image in which each area contains almost all the information about the entire system. It is a metaphor commonly used for complex systems in which the whole is bigger than the sum of the parts because of self-organization. And also the whole is smaller than the sum of the parts, since the collective organization limits the behavior of dynamic features. The tectonic evolution of the Earth is an emergent behavior of the lithosphere-mantle system, a witness of a program defined at the scale of rocks. Modeling the physics behind tectonics at a global scale became a reachable goal entering the 21st Century. Geodynamicists developed numerical models of solid-sate convection with yielding, and reproduced some fundamentals of planetary tectonics. In the past 15 years, several groups in the world have used these models to investigate how continents drift, seafloor spreads and plates evolve. These emergent characteristics tell that the whole is bigger than the sum of the parts. Slabs, plumes, ridges, plates are interdependent and constrain each other. The whole is smaller than the sum of the parts. In this context, searching for causality relationships between tectonic features seems vain. In this chapter, I consider this point of view to describe how convection models with yielding have changed and still change our views on how tectonics shape the Earth. I finally propose an outlook about this window that remains half-opened.