Plate tectonics has been the major unifying theory in geosciences for the last 40 years. By linking the evolution of the Earth’s surface to the dynamics of the deep Earth, it has provided a coherent framework to understand the formation of mountain ranges and oil-rich sedimentary basins, as well as the distribution of major catastrophic events such as volcanic eruptions and earthquakes. Yet, until recently, mantle convection and plate tectonics have been studied as independent systems. In convection studies, plates were generally considered as rigid rafts dragged along by the convecting mantle. On the other hand, "lithospheric" studies focused on the petrological evolution and on the deformation of the crust, often neglecting even the lithospheric mantle. This duality is now over. The last decade has seen a clear evolution. We now understand that plate tectonics is an essential feature of mantle convection. However, the processes allowing convection in the mantle to produce plate tectonics at the Earth's surface as well as many aspects of the interaction between the convective flow and the plates remain poorly understood.

How does plate tectonics actually work? To answer this question, the CRYSTAL2PLATE Initial Training Network will study the interactions between lithospheric plates and the convecting mantle. The research projects will investigate: (1) how plates modify or are affected by convection, (2) the role of the preexisting structure of the plates on the deformation distribution, (3) the coupling between chemical and physical processes, in particular through partial melting, fluids percolation, and fluid-rock reactions. Linking chemical and physical processes in the mantle requires understanding the relation of crystal-scale processes to the large-scale dynamics. Crystal- and rock-scale processes, such as viscous and elastic deformation, melt transport and reactions, modify the composition, microstructure, and physical properties of mantle rocks, which are the key for interpreting geophysical observations in terms of temperature, composition, and deformation in the mantle. On the other hand, small-scale processes depend on the large-scale temperature, stress, and pressure structure in the mantle. Understanding the interactions between physical and chemical processes at various scales in the mantle is thus fundamental to comprehend its dynamics and hence the onset of plate tectonics.

The primary objectives of CRYSTAL2PLATE are:

1. to advance our understanding of how mantle convection produces, and is modified by, plate tectonics by fully taking into account the interactions between physical and chemical processes as well as between crystal-scale processes and large-scale dynamics in the mantle;

2. to train 10 early-stage researchers (ESRs) and 2 experienced researchers (ERs) in state-of-the-art concepts and leading-edge research techniques that are essential to study the behaviour of complex natural systems, while providing them strong career-management skills and solid professional connections;

3. to increase the impact and international visibility of European research by structuring the research training capacities in Geodynamics via the establishment of a long-term collaboration and synergy among 7 research teams internationally recognized for their excellence in complementary fields of Earth Sciences: tectonics, mineral physics, petrology, geochemistry, seismology, and geodynamic modelling.

The main innovation of CRYSTAL2PLATE is the focus on three different modes of interaction in the mantle:

1. between small- and large-scale processes,

2. between physical and chemical processes at the crystal and rock-scale, and,

3. at the larger scale, between the plates and the convecting mantle.

The study of the coupling between the plates and the convecting mantle based on the analysis of the interactions between physical and chemical processes and between crystal-scale processes and large-scale dynamics provides a rich training ground for young scientists. It is a highly pluridisciplinary research field at the convergence between geology, geochemistry, geophysics, petrology, fluid mechanics, and mineral physics. It introduces them to the diversity of processes controlling the evolution of our planet and the challenges of unravelling this complexity through the association of techniques from different disciplines, whilst at the same time giving them an opportunity to engage in an area of research that can make a real contribution to our understanding of the processes involved in the evolution of the Earth and other telluric planets. The physical, chemical, computer modelling skills as well as the team-building, management, and mobility experience gained in CRYSTAL2PLATE will open up research careers in academia or in industry, as these skills can be applied in a variety of situations where analytical aptitude to deal with complex data sets and acquisition of accurate information are required.