Geodynamics

It applies physics, chemistry and mathematics to the understanding of how mantle convection leads to plate tectonics and geologic phenomena such as seafloor spreading, mountain building, volcanoes, earthquakes, faulting.

It also attempts to probe the internal activity by measuring magnetic fields, gravity, and seismic waves, as well as the mineralogy of rocks and their isotopic composition.

Rocks are structurally and compositionally heterogeneous and are subjected to variable stresses, so it is common to see different types of deformation in close spatial and temporal proximity.

[4] Experts in geodynamics commonly use data from geodetic GPS, InSAR, and seismology, along with numerical models, to study the evolution of the Earth's lithosphere, mantle and core.

Since, over long periods, rocks readily deform under pressure, the Earth is in hydrostatic equilibrium to a good approximation.

If stress exceeds the yield strength of a material, bonds begin to break (and reform), which can lead to ductile or brittle deformation.

[5] Ductile deformation happens when transport processes such as diffusion and advection that rely on chemical bonds to be broken and reformed redistribute strain about as fast as it accumulates.

[7] The main motive force behind stress in the Earth is provided by thermal energy from radioisotope decay, friction, and residual heat.

Close to the surface of the Earth, data includes field observations, geodesy, radiometric dating, petrology, mineralogy, drilling boreholes and remote sensing techniques.

Because of the complexity of geological systems, computer modeling is used to test theoretical predictions about geodynamics using data from these sources.

[14] Basic fluid dynamics modelling can further be subdivided into instantaneous studies, which aim to reproduce the instantaneous flow in a system due to a given buoyancy distribution, and time-dependent studies, which either aim to reproduce a possible evolution of a given initial condition over time or a statistical (quasi) steady-state of a given system.

Figure 2 shows a Rayleigh-Taylor instability in 2D using the Shan-Chen model . The red fluid is initially located in a layer on top of the blue fluid, and is less buoyant than the blue fluid. After some time, a Rayleigh-Taylor instability occurs, and the red fluid penetrates the blue one.