Laboratoire Last Day On Earth
Raingarda Krzynowek
Typical questions under investigation are, for example:
- the question of the emergence and sustainability of plate tectonics on Earth;
- Crystallization of the early Mantle and long-term existence of a Basal Magma Ocean;
- Dynamics of the inner core, compatible with seismic anisotropy and hemispherical asymmetry;
- Accretion/differenciation of the Earth.
My research interests are covering different aspects of planetary dynamics: the dynamo effect in the Earth's core, dynamics and thermodynamics of the inner core, of the early mantle and compressible convection. Using analogue experiments and numerical modelling, I have been studying crystallization processes in the dendritic regime, with applications to the crystallization of the inner core (PhD of Ludovic Huguet, collaboration with Michael Bergman). In particular, with Renaud Deguen, we have identified a mechanism of convective translation of the inner core, as a result of the interaction between phase change, heat transfer in the outer core, convection in the inner core and self-gravitational equilibrium. We are working on a similar dynamics for the early mantle crystallization with Stephane Labrosse and Adrien Morison. More recently, my research has been focused essentially on compressible effects in convection. With Remi Menaut (PhD), we are investigating experimental compressible effects in a centrifuge. Increased gravity is also accompanied by Coriolis effects (PhD of Yoann Corre). I am also interested in theoretical aspects of compressible convection: with Yanick Ricard, we have analyzed different equivalent expressions for the viscous dissipation and we have performed a comprehensive stability analysis of compressible convection, valid for any physically sound equation of state. With Stephane Labrosse, Yanick Ricard and Jezabel Curbelo (Spanish collaboration), we are analyzing numerical compressible convection with different approximation levels, from an "exact model" (Navier-Stokes, equation of state, entropy equation) to a Boussinesq solution, with intermediate anelastic models.
I am a geodynamicist using numerical modelling to bridge theoretical models with observations. I had the chance to explore various fields of geosciences, from geochemistry of the carbon cycle, to sedimentology of Archean basins, or global tectonics. These past years, I have been focused on the AUGURY project (www.augury.eu), which aims at building inverse methods to realise tectonic reconstructions. The particularity of the approach is our use of convection models producing plate-like behaviour self-consistently. We develop data assimilation codes (sequential and variational) starting from the code StagYY initiated by Paul J. Tackley (ETH Zurich), and using the data base of the EarthByte group in Sydney.
My research focuses on the dynamics and evolution of the deep Earth from its earliest stages to recent times, with a particular focus on the thermal evolution. This includes modelling of the thermal and chemical evolution of the core, inner core growth, mantle convection. In the recent years, I have focused more on processes related to the early deep Earth: core formation, magma ocean dynamics and evolution, solid mantle convection interacting with magma oceans. I address these issues mostly using thermodynamics and theoretical and numerical models of fluid dynamics.
I am a terrestrial and planetary volcanologist. The originality of my research consists in the coupling between sophisticated fluid dynamics models with spatial observations and data analysis. Lately I have been interested in the filtering role planetary crusts exert on the ascent, storage and eruption of magmas. To that aim, I have developed models and tools to look for cryomagma and solidified magma reservoirs in planetary ice shells and crusts. I am also interested in the early processes of terrestrial crust formation and evolution. I am currently studying the effects of impact cratering on magma ascent and magma reservoir formation.
I am interested in how the interactions between the lithosphere and the mantle shape the Earth's surface. I work with numerical models to understand the mecanisms behind plate velocities and lithospheric stresses, including the formation of topography. One of my projects aims at better understanding the net rotation of the lithosphere with respect to the lower mantle using 3D spherical models where plate boundaries evolve self-consistently (in collaboration with Nicolas Coltice). My other project aims at coupling a 2D geodynamic code with a Markov chain Monte Carlo approach in order to determine the physical properties of the Mexican subduction zone, where the subduction is flat and a large earthquake recently occurred (in collaboration with Thomas Bodin).
I am working on the dynamics of the primitive Earth mantle. Due to the heat brought by impacts, radiogenic heating, and core differentiation, the primitive mantle may have been totally melted, forming a magma ocean. Depending on the temperature profile and the shape of the solidus in this magma ocean, the crystallization of the solid mantle may have started from the bottom or the middle of the magma ocean. This leads to the formation of a solid spherical shell with magma oceans above and/or below. Convecting matter in the solid shell can cross the boundary between the solid shell and the magma ocean by melting and freezing. This phenomenon is parametrized with a boundary condition applied to the creeping flow in the solid. I study the effects of this boundary condition on the convection in the solid.
The main focus of my research is to develop models of mantle convection self-generating plate tectonics, using the StagYY numerical code from P. Tackley, in order to study and understand the interactions between mantle dynamics and its surface expressions on Earth. I am more particularly investigating the spatial and temporal evolution of dynamic topography in those numerical models in order to compare it with Earth observations and understand from which processes it originates. Another project is to study the dynamics of mantle plumes in 3D models of mantle convection with plate tectonics in order to understand how their interactions with the surface can cause them to move laterally. I collaborate with geologists from the EarthByte group at the University of Sydney and the University of Wollongong in Australia in order to help to improve reconstructions of the past locations of continents on Earth thanks to the physics of my models.