Modelling moving force of tectonic plates with the use of length of day variation

Abstract

<p>The nature, the age and probably first of all the magnitude of driving forces of plate motion since long are a subject of scientific debates and it cannot be regarded as clarified even today.</p><p>The physical basis of recent plate tectonics is characterized by interaction between plates by viscous coupling to a convecting mantle.  Authors are going to demonstrate that changes in the Earth's axial rotation can affect the movement of tectonic plates, and the phenomenon of tidal friction is able to shift the lithospheric plates.</p><p>The tidal friction regulates the length of day (LOD)and consequently also the rotational energy of the Earth. It can be investigated with the use of total tidal energy<sub>, </sub>which can be determined as a sum of three energies (energy of axial rotation of the Earth, Moon’s orbital energy around the common centre of mass and the mutual potential energy). It was found that during the last 3 Ga the Earth lost 33% of its rotational energy. The LOD 0.5Ga BP (before present) was ~21 h. This means that the rotational energy loss rate was 4.1 times higher during the Pz (Phanerozoic, from 560 Ma BP to our age) than earlier in the Arch (Archean, 4 to 2.5 Ga BP) and Ptz (Proterozoic 2.5 to0.56 Ga BP). The low-velocity zone (LVZ) at 100-200 km depth interval, close to the boundary between the lithosphere and the asthenosphere characterized by a negative anomaly of shear wave velocities. Consequently, the LVZ can result in a decoupling effect. Tidal friction brakes the lithosphere and the part of the Earth below the asthenosphere with different forces. By model calculation, we show that this force difference is sufficient to move the tectonic plates along the Earth’s surface.  </p><p>Reference: Varga P., Fodor Cs., 2021. About the energy and age of the plate tectonics, Terra Nova. (in print) https://doi.org/10.1111/ter.12518</p>