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An Explanation for Earth's Long-Term Rotational Stability
Richards1, Ricard, Lithgow-Bertelloni
1M. A. Richards, Department of Geology and Geophysics, University of California, Berkeley, CA 94720, USA. Y. Ricard, Departement de Geologie, Ecole Normale Superieure, Lyon, France. C. Lithgow-Bertelloni, Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015-1305, USA. G. Spada, Dipartimento di Fisica, Settore Geofisica, Universita di Bologna, Bologna, Italy. R. Sabadini, Dipartimento di Scienze della Terra, Sezione Geofisica, Universita di Milano, Milano, Italy.
Earth's rotation axis has been stable for 100 million years, with minimal true polar wander. Plate tectonic motion, particularly subducted lithosphere, explains this stability without needing other mechanisms.
Area of Science:
- Geophysics
- Paleomagnetism
- Plate Tectonics
Background:
- Paleomagnetic data indicate minimal motion between paleomagnetic and hotspot reference frames over the past 100 million years.
- This suggests a stable Earth rotation axis, a phenomenon requiring explanation within geological timescales.
Purpose of the Study:
- To investigate the causes of long-term rotational stability of Earth.
- To determine if plate tectonic motion can account for the observed low rate of true polar wander.
Main Methods:
- Analysis of paleomagnetic data to reconstruct past plate motions.
- Modeling of mantle convection and density heterogeneity, considering subducted lithosphere.
Main Results:
- Less than 1000 km of motion observed between paleomagnetic and hotspot frames over 100 million years.
- Plate tectonic motion patterns during the Cenozoic and late Mesozoic show slow changes.
- Subducted lithosphere is identified as a significant contributor to mantle density heterogeneity.
Conclusions:
- Earth's rotational stability is explained by the slow evolution of plate tectonic motions.
- Subducted lithosphere's role in mantle convection adequately accounts for the low rate of true polar wander.
- Additional mechanisms like rotational bulge readjustment are not necessary to explain observed stability.