Viscosity of hcp iron at Earth's inner core conditions from density functional theory.

The inner core, extending to 1,221 km above the Earth's center at pressures between 329 and 364 GPa, is primarily composed of solid iron. Its rheological properties influence both the Earth's rotation and deformation of the inner core which is a potential source of the observed seismic anisotropy. However, the rheology of the inner core is poorly understood.

Pure climb creep mechanism drives flow in Earth's lower mantle.

At high pressure prevailing in the lower mantle, lattice friction opposed to dislocation glide becomes very high, as reported in recent experimental and theoretical studies. We examine the consequences of this high resistance to plastic shear exhibited by ringwoodite and bridgmanite on creep mechanisms under mantle conditions. To evaluate the consequences of this effect, we model dislocation creep by dislocation dynamics.