Showing papers by "Nicolas Coltice published in 2022"

Tectonics is a hologram

Abstract: 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.

Tectonics is a Hologram

Abstract: 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 lithospheremantle 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 ∗Corresponding author. Email address: nicolas.coltice@ens.fr (Nicolas Coltice ) Published as Dynamics of Plate Tectonics and Mantle Convection November 4, 2022 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.

True polar wander and heat flux patterns at the core-mantle boundary in a mantle convection simulation

Abstract: . The core-mantle boundary (CMB) heat flux is an important variable of Earth’s thermal evolution and dynamics. Seismic tomography enables access to seismic heterogeneities in the lower mantle, which can be related to present-day thermal heterogeneities. Alternatively, mantle convection models can be used to either infer the past CMB heat flux or to produce statistically realistic CMB heat flux distributions in self-consistent models. Mantle dynamics modifies the inertia tensor of the Earth, which implies a rotation of the Earth with respect to its rotation axis called True Polar Wander (TPW). This rotation 5 has to be taken into account if mantle dynamics is to be linked to core dynamics. In this study, we explore the TPW and the CMB heat flux produced by a self-consistent mantle convection model. The geoid is also computed and investigated in order to determine the driving mechanism of TPW. This model includes continents, dense chemical piles at the bottom of the shell and plate-like behavior, providing the possibility to link TPW and the CMB heat flux with plate tectonics. A principal component analysis (PCA) of the CMB heat flux is computed to obtain the dominant heat flux patterns. The model shows a 10 geoid dominated by upper mantle structures. Subduction zones and continents are correlated with positive geoid anomalies, about 20 times larger than the observed geoid anomalies. Chemical piles are mostly correlated with negative geoid anomalies because of the anti-correlation between the positions of subducting slabs and the piles. TPW thus tends to lock continents and subduction zones close to the equator, while chemical piles are shifted towards higher latitudes. The positive CMB heat flux anomalies are mostly located at low

An overview of modeled dynamic histories of rocky planets

Abstract: <p>Every planet is singular, with scars and bumps at their surface. One planet, one history. But the physics at play is common to them, connecting planetary bodies together. Tectonics is a common theme of what we can observe on planets of the solar system, and a central question for explanets. More than 20 years of geodynamic modelling has resulted in  identifying a diversity of tectonic regimes for mantle convection, from very active, like heat-pipe (Monnereau and Dubuffet, 2002 among others) and squishy lid (Lourenço et al., 2020) to almost inert, like stagnant lid (Schmeling and Jacoby, 1982). Tectonics is an emergent property deriving from the intimate structure and composition of a planet. It is also a fundamental piece shaping the surface environment. This presentation will attempt to give an overview of tectonic regimes of planets and propose typical evolutional scenari, connecting structural and compositional histories from the depth to the surface.</p><p> </p><p><strong>References</strong></p><p>Lourenço, D. L., Rozel, A. B., Ballmer, M. D., & Tackley, P. J. (2020). Plutonic‐squishy lid: A new global tectonic regime generated by intrusive magmatism on earth‐like planets. Geochemistry, Geophysics, Geosystems, 21, e2019GC008756.</p><p>Monnereau, M., & Dubuffet, F. (2002). Is Io's mantle really molten?. Icarus, 158, 450-459.</p><p>Schmeling, H., & Jacoby, W. R. (1982). On modelling the lithosphere in mantle convection with non-linear rheology. Journal of Geophysics, 50, 89-100.</p>