Earth is undergoing true polar wander, scientists say

Subject: 
Earth is undergoing true polar wander, scientists say
Posted By: 
Cosmic Observer
Date: 
Wednesday, October 03, 2012 12:25 pm

 

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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 117, B09101, 30 PP., 2012
doi:10.1029/2011JB009072

Absolute plate motions in a reference frame defined by moving hot spots in the Pacific, Atlantic, and Indian oceans
Absolute plate motions in a reference frame defined by moving hot spots in the Pacific, Atlantic, and Indian oceans
Key Points

* A fully self-consistent refrence frame for absolute plate reconstructions
* Fixed hot spot models produce unacceptable misfits for the 80-50 Ma interval
* True polar wander has been slow but significant for the past 120 Ma

Pavel V. Doubrovine

Physics of Geological Processes, University of Oslo, Oslo, Norway

Center for Advanced Study, Norwegian Academy of Science and Letters, Oslo, Norway

Bernhard Steinberger

Physics of Geological Processes, University of Oslo, Oslo, Norway

Center for Advanced Study, Norwegian Academy of Science and Letters, Oslo, Norway

Helmholtz Center Potsdam, GFZ German Research Center for Geosciences, Potsdam, Germany

Trond H. Torsvik

Physics of Geological Processes, University of Oslo, Oslo, Norway

Center for Advanced Study, Norwegian Academy of Science and Letters, Oslo, Norway

Center for Geodynamics, Geological Survey of Norway, Trondheim, Norway

School of Geosciences, University of Witwatersrand, Johannesburg, South Africa

We defined a new global moving hot spot reference frame (GMHRF), using a comprehensive set of radiometric dates from arguably the best-studied hot spot tracks, refined plate circuit reconstructions, a new plate polygon model, and an iterative approach for estimating hot spot motions from numerical models of whole mantle convection and advection of plume conduits in the mantle flow that ensures their consistency with surface plate motions. Our results show that with the appropriate choice of a chain of relative motion linking the Pacific plate to the plates of the Indo-Atlantic hemisphere, the observed geometries and ages of the Pacific and Indo-Atlantic hot spot tracks were accurately reproduced by a combination of absolute plate motion and hot spot drift back to the Late Cretaceous (∼80 Ma). Similarly good fits were observed for Indo-Atlantic tracks for earlier time (to ∼130 Ma). In contrast, attempts to define a fixed hot spot frame resulted in unacceptable misfits for the Late Cretaceous to Paleogene (80–50 Ma), highlighting the significance of relative motion between the Pacific and Indo-Atlantic hot spots during this period. A comparison of absolute reconstructions using the GMHRF and the most recent global paleomagnetic frame reveals substantial amounts of true polar wander at rates varying between ∼0.1°/Ma and 1°/Ma. Two intriguing, nearly equal and antipodal rotations of the Earth relative to its spin axis are suggested for the 90–60 Ma and 60–40 Ma intervals (∼9° at a 0.3–0.5°/Ma rate); these predictions have yet to be tested by geodynamic models.

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