The co-evolution of mantle and core over Earth’s history

• Applicant: Dr. Nicola Tosi
• Subject Area: Geophysics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 521319695

Seismic observations offer a snapshot of the structure, thermal state and composition of the Earth’s core as it is today, while paleomagnetic measurements place fundamental constraints on the existence, intensity and characteristics of the dynamo-generated magnetic field over geological timescales, from the Archean to the present. For a given core structure, numerical models of the geodynamo provide insight into the mechanisms of magnetic field generation over timescales of up to millions of years, while the global evolution of the core is controlled primarily by heat extracted by the solid mantle, which operates on timescales of hundreds of millions to billions of years. Understanding the structure, thermal and compositional state of the core, at present and over time, requires insight from theoretical models of the coupled evolution of the core-mantle system. Existing models of the evolution of the core over Earth’s history are already highly advanced. However, in these models the role of the mantle is often overlooked, being limited to simple thermal histories that circumvent the complexities and large uncertainties related to the efficiency with which the mantle has been driving the cool-ing of the core and its solidification. Furthermore, most models neglect the effects of the solidification of a putative basal magma ocean (BMO), whose existence is required by essentially all core models in order to satisfy the numerous constraints associated with the evolution of the geomagnetic field and present-day state of the core. In this project, we will develop a comprehensive one-dimensional numerical model of the coupled thermo-chemical evolution of solid mantle, BMO and core over Earth’s history. We will employ observational constraints on the core structure, composition, evolution and thermal proper-ties derived from seismology, paleomagnetism, magnetic field modelling, and mineral physics. In parallel, we will consider geological, petrological and mineral-physics constraints on the composition and evolution of the silicate mantle and their influence on the core. We will thus deliver a coherent description of the long-term evolution of the deep interior, elucidating the coupling between mantle and core and disclosing the numerous trade-offs caused by the large uncertainties in model pa-rameters and poorly known processes associated with the thermo-chemical history of the two major reservoirs of the Earth.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2404: Reconstructing the deep dynamics of planet Earth over geologic time (DeepDyn)
• Co-Investigators: Professorin Dr. Doris Breuer; Dr. Tina Rückriemen-Bez