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| Titel |
Plate tectonics conserves angular momentum |
| VerfasserIn |
C. Bowin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1815-381X
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| Digitales Dokument |
URL |
| Erschienen |
In: eEarth ; 5, no. 1 ; Nr. 5, no. 1 (2010-03-24), S.1-20 |
| Datensatznummer |
250002265
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| Publikation (Nr.) |
 copernicus.org/ee-5-1-2010.pdf |
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| Zusammenfassung |
A new combined understanding of plate tectonics, Earth internal structure,
and the role of impulse in deformation of the Earth's crust is presented.
Plate accelerations and decelerations have been revealed by iterative
filtering of the quaternion history for the Euler poles that define absolute
plate motion history for the past 68 million years, and provide an
unprecedented precision for plate angular rotation variations with time at
2-million year intervals. Stage poles represent the angular rotation of a
plate's motion between adjacent Euler poles, and from which the maximum
velocity vector for a plate can be determined. The consistent maximum
velocity variations, in turn, yield consistent estimates of plate
accelerations and decelerations. The fact that the Pacific plate was shown
to accelerate and decelerate, implied that conservation of plate tectonic
angular momentum must be globally conserved, and that is confirmed by the
results shown here (total angular momentum ~1.4+27 kg m2 s−1). Accordingly, if a plate decelerates, other plates must
increase their angular momentums to compensate. In addition, the azimuth of
the maximum velocity vectors yields clues as to why the "bend" in the
Emperor-Hawaiian seamount trend occurred near 46 Myr. This report summarizes
processing results for 12 of the 14 major tectonic plates of the Earth
(except for the Juan de Fuca and Philippine plates).
Plate accelerations support the contention that plate tectonics is a product
of torques that most likely are sustained by the sinking of positive density
anomalies revealed by geoid anomalies of the degree 4–10 packet of the
Earth's spherical harmonic coefficients. These linear positive geoid
anomalies underlie plate subduction zones and are presumed due to phase
changes in subducted gabbroic lithosphere at depth in the upper lower mantle
(above 1200 km depth). The tectonic plates are pulled along by the sinking
of these positive mass anomalies, rather than moving at near constant
velocity on the crests of convection cells driven by rising heat. The
magnitude of these sinking mass anomalies is inferred also to be sufficient
to overcome basal plate and transform fault frictions. These results imply
that spreading centers are primarily passive reactive features, and fracture
zones (and wedge-shaped sites of seafloor spreading) are adjustment zones
that accommodate strains in the lithosphere. Further, the interlocked
pattern of the Australian and Pacific plates the past 42 Million years (with
their absolute plate motions near 90° to each other) is taken as
strong evidence that large thermally driven "roller" convection cells
previously inferred as the driving mechanism in earlier interpretations of
continental drift and plate tectonics, have not been active in the Earth's
mantle the past 42 Million years, if ever.
This report also presents estimates of the changes in location and magnitude
of the Earth's axis of total plate tectonic angular momentum for the past 62
million years. |
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