Dynamical motions within the core are responsible for generating the Earth's magnetic field by way of dynamo action and in Dynamics of the Core, Geodynamo , Paul Roberts describes recent, mostly theoretical efforts to shed light on how the core dynamo works. Related papers on geomagnetism and paleomagnetism are in the section on Properties of the Solid Earth. Deformation of the crust and mantle is controlled by the rheological behavior of the rocks in these regions of the Earth. Brittle behavior is responsible for shallow faulting and earthquakes, while ductility allows rocks to deform in a fluid-like manner over geologic time. Faults have a distinctive rheology that new studies have shown to depend importantly on fluid flow.
Fault friction is a controlling factor in the occurrence of earthquakes.
Brittle behavior cannot explain the occurrence of earthquakes deep in the mantle. Some other mechanism, perhaps transformational faulting related to the occurrence of the phase change from metastable olivine to spinel within the transition zone of the mantle, must be responsible as discussed by Stephen Kirby in the paper already referenced above. Magellan opened Venus to our scrutiny with its radar and for the first time we have knowledge of the planet's geology, topography, and gravity at relatively high resolution and on a global basis. A New View of Venus Geology and Geophysics . Improvements in our knowledge of the gravity field of Venus and other planets, including Earth, Mars, and the Moon are summarized in Terrestrial and Planetary Gravity Fields by R. Steven Nerem.