Plate tectonics and mantle convection are critical for Earth鈥檚 habitability. They impact Earth鈥檚 climate through the deep carbon cycle and control sea level changes, and many of Earth鈥檚 most destructive natural hazards - earthquakes, volcanic eruptions, and tsunamis - are associated with plate boundaries. But despite this immense importance, major questions about the operation of the coupled system of plate tectonics and mantle convection remain unresolved. What are the magnitudes of forces driving and resisting plate tectonics? How do new subduction zones overcome the internal strength of plates? What controls localization of deformation along plate boundaries over geological time? And how do changes in plate motions and mantle convection affect the Earth鈥檚 magnetic field?
The goal of the 鈥楥omputational Geodynamics鈥� group is to understand the dynamics of tectonic plates and the convecting mantle below, with a focus on oceanic plates and their creation, evolution, and recycling through the Earth鈥檚 interior. For that purpose, we develop mathematical and computational process models that can help us understand how these processes have shaped the evolution of Earth鈥檚 surface. We use high-performance computing and modern research software to implement these models, to create testable predictions, and to compare them to observations.
Integrating physical processes across scales
A key approach to deciphering mechanisms of the plate/mantle system and its interaction with the Earth鈥檚 surface is connecting the plate tectonic scale to the microscale. This is because mechanisms acting on the length scale of the mineral grains that make up rocks determine how rocks are deformed on the regional and global scale. Therefore, one of the goals of the 鈥楥omputational Geodynamics鈥� group is to integrate these microscale models of grain-scale deformation in mantle convection and lithosphere deformation simulations. Examples include the importance of grain size evolution for global convection patterns and the role of grain damage in the collapse of passive margins.
The image shows how the mineral grain size affects the viscosity in and around subducted slabs in a global convection model. Changes in viscosity due to grain size variations are comparable to the ones caused by temperature.
Magma generation and dynamics
We are interested in where magma forms in the Earth, how it moves to the surface, and the role it plays in volcanic eruptions. For this purpose we develop numerical methods that allow us to model the porous flow of magma through a deforming solid rock using the modeling software . We have applied this method in computer simulations of mid-ocean ridges and magma generation and transport at the core-mantle boundary.
The image shows a model of a mid-ocean ridge, with the red-yellow-white streamlines illustrating the flow of magma.
Mantle plumes and their interaction with tectonic plates
The Earth鈥檚 biggest magmatic events are believed to originate from massive melting when hot mantle plumes rising from the lowermost mantle approach the surface. The associated volcanic eruptions are thought to be related to environmental catastrophes and mass extinction events. After this first pulse of magmatic activity, plume conduits can remain stable in the mantle for hundreds of millions of years, generating hotspot volcanism.
We are interested in the effect of the chemical heterogeneity of the Earth鈥檚 mantle on plume dynamics, the interplay between subducted oceanic plates, chemical reservoirs in the deep mantle and rising plumes, and how these processes influence hot spot volcanism observed at the Earth鈥檚 surface.
The image shows a model of a mantle plume, computed with the code.
Coupling geodynamics and thermodynamics
While geodynamic models can tell us about how Earth materials deform and how forces acting in the Earth鈥檚 interior will shape its evolution, in order to be able to do that, they need the thermodynamic properties of rocks - describing their density, how rocks expand or compact under changes in temperature or pressure, and which minerals are stable for a given composition, temperature and pressure. Including these thermodynamic models into geodynamic simulations can be complex and poses a number of challenges. Developing new methods to address this challenge is one of the goals of the 鈥楥omputational Geodynamics鈥� group. Examples include new approximations for modeling compressibility, and using entropy instead of temperature to more accurately model mineral phase transformations.
The image shows different convection models with the same setup with a phase transition with a negative Clapeyron slope at mid depth, except that the width of the phase transition decreases from the left to the right panel. This results in a change in convective regime.
Global plate-tectonic models
The coupled system of plate tectonics and mantle convection is critical for Earth鈥檚 habitability, controlling the cycling of elements such as carbon through the Earth鈥檚 deep interior and providing a source of power for the geodynamo that creates the Earth鈥檚 magnetic field. However, understanding plate motions is a challenge due to the interaction of global mantle flow and local plate boundary processes. The 鈥楥omputational Geodynamics鈥� group studies global plate motions and plate boundary strength by facilitating the integration of advanced datasets into global deformation models, and we investigate how plate motions and global convection affect variations in the magnetic field by linking the output of our simulations to geodynamo models.
The image shows a global mantle convection model, computed with the code.
Prof. Juliane Dannberg
Group Leader
Dr. Rene Gassm枚ller
Staff Scientist
Ranpeng Li
Doctoral Researcher
Sandra Spahl
Team Assistant
To be able to study the dynamics of the Earth鈥檚 interior, we develop the free community software (Advanced Solver for Planetary Evolution, Convection and Tectonics). uses modern numerical methods to support research in modeling the dynamics of the Earth鈥檚 mantle and crust as well as the dynamics of other planetary bodies. Our goal with is to provide the geosciences with a well-documented and extensible code base for their research needs. Its flexibility has allowed its application in studies of global and regional mantle convection, plume and subduction dynamics, lithosphere and crustal dynamics, rifting, resource formation, inner core dynamics, deformation of Mars, Venus, the Moon and icy satellites. Modern software development techniques make equally efficient in 2D and 3D, and its solver scales up to more than 110,000 cores on Frontera, the largest HPC system of the US National Science Foundation cyberinfrastructure.
2024 鈥淭he life cycle of oceanic plates: From the grain scale to the global scale鈥�
(Funding of first-time professorial appointments of excellent women scientists by the Helmholtz Association, Juliane Dannberg)
