New Mechanisms for Plate Tectonics, Lunar Drift, and Differential Rotation of the Lithosphere

Anne Hofmeister, Washington University in St. Louis

Innumerable examples exist in the Universe whereby motions of large objects are driven by gravitational forces. Yet, motions of Earth’s lithospheric plates have been attributed to internal radioactive heat that allegedly churns the strong solid mantle. Insufficiency of this mechanism to such a task is widely recognized. Similarly, lunar drift is attributed to angular momentum of Earth’s spin being transferred across space, which impossibly requires gravitational isolation of the Earth and Moon from the Sun: moreover, the isolated 2-body system lacks torque.

Force imbalances within the Earth-Moon-Sun system cause lunar drift and the conspicuous asymmetries of plate tectonics. The Moon following a path crossing the plane of the barycenter orbit creates the torque required to alter its orbital angular momentum. A perturbation model provides a recessional velocity in good agreement with ranging data.

Earth's geocenter follows a subdued and opposite path, providing the time-and space-dependent torque required for motions among the plates. Importantly, plate tectonics is superimposed on differential rotation of the whole lithosphere (aka westward drift, demonstrated by paleontologic and seismologic evidence). Spin down is ubiquitous among astronomical objects, because surface layers of oblate stars and planets are relatively cold and stiff, due to radiation to space outpacing conduction. Earth is still active because the forces in the complex Earth-Moon-Sun system pump in energy.

Top-down heating and tectonics is consistent with 1) production of spin, not heat, during cold accretion; 2) differentiation of only the outer 10% of Earth; 3) time-dependent, co-accretion of the Solar System; and 4) very early formation of Earth's core.  Mechanical causes are cold welding and magnetic attraction supplementing gravitational of iron dust in the pre-solar nebulae. Lastly, Hofmeister will briefly present evidence for chondrules and chondrites being aeolean deposits formed in the winds of accretion. This depiction of Earth and its formation is consistent with both physical principles and observational evidence. Details are presented in my 2019 and 2020 books.