Mathematics – Logic
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.u13a0868r&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #U13A-0868
Mathematics
Logic
1213 Earth'S Interior: Dynamics (1507, 7207, 7208, 8115, 8120)
Scientific paper
On geological timescales, True Polar Wander (TPW) is due to surface loads and mass deficits or mass rearrangement within the mantle, which disturbs the inertia of the planet. Earth presents a complex and changing distribution in density. Subducted plates are evident producers of these heterogeneity in the mantle. The history of density heterogeneities due to cold plates diving through the mantle has been reconstructed for the past 120 Myr by Ricard et al. (1993). After this work, we calculate the induced perturbations of the inertia tensor and their effect on the spin axis. But the computed wander appears large and lacking features comparing with paleomagnetic observations (Besse & Courtillot, 2002). Greff-Lefftz (2004) showed that the doming regime is the only upwelling structure able to produce large TPW as subducted plates do. We add the inertial perturbations due to simple models of the African and the Pacific superplumes to the ones due to subducted plates in order to see if they can stabilize the rotation pole at relatively high latitudes (paleomagnetism stands the pole between 60 and 90 degrees of latitude during the last 200 Myr). But the distribution of superplumes (one under each pacific and african hemisphere, in the lower mantle) imposes a position for their axis of maximum inertia roughly close to northern Atlantic. That is to say the superposition of the inertial effects due to subducted plates and doming regime would carry the pole in the atlantic area, towards the equator. Besides, a large amount of small plumes rises through the upper mantle on top of the superplumes. They should induce TPW along a meridian joining the two pacific and african hemispheres. We check off these plumes during the last 200 Myr. Modelling them simply, we take into account the perturbations of the inertia they induced in order to know if they are the essential component to stabilize the rotation pole as they are to explain the current geoid.
Besse Jean
Greff-Lefftz Marianne
Rouby Hélène
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