The origin of geoid and topography anomalies of the Tharsis rise

Details The origin of geoid and topography anomalies of the Tharsis rise The origin of geoid and topography anomalies of the Tharsis rise

Apr 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eaeja.....4460z&link_type=abstract

EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #4460

Other

Scientific paper

The long-wavelength gravity and topography (degrees 2-4) anomalies on Mars can be attributed to the Tharsis Rise. It is therefore important to understand the origin of the Tharsis geoid and topography anomalies. Two competing models have been proposed: 1) surface processes including volcanic construction and its associated lithospheric flexural effects, and 2) mantle convection associated with an ascending thermal plume. In this study we seek to distinguish between these two competing models. Such an attempt becomes feasible with recent studies that provide a more robust estimate of elastic thickness Te in the Tharsis region [McGovern et al., 2002] and that indicate a significant reduction in the estimate of long-wavelength geoid from a plume due to elastic flexural effects [Zhong, 2002] that were ignored in previous plume models of Tharsis. We use ratio of geoid to topography (GTR) at degrees 2-4 to constrain the possible contribution from plume buoyancy to the Tharsis geoid and topography anomalies. Our models assume that the Tharsis anomalies result from combining effects of surface loading and plume buoyancy loading at different depths. Two controlling model parameters are Te and plume buoyancy depth Dp. Since long-wavelength components of plume buoyancy only occur below lithosphere where plume material spreads out, we recast Dp as a multiple of Te (i.e., Dp=fTe, where f is a multiplier). In our approach, first, GTR for surface loading is computed for different Te. Second, GTR for plume buoyancy loading is computed for different Te and f. Third, using the dependence of GTR on Te for surface and internal loadings, we solve for the Te-dependence of the fraction of observed geoid and topography attributable to plume buoyancy, for a given multiplier f and harmonic degree. For reasonable elastic parameters and densities for the crust and mantle, we found that at degrees 2 and 3, surface loading with Te˜100 km nearly explains all the observed geoid and topography anomalies with no need to invoke plume buoyancy. For other possible Te, contribution from internal loading is necessary. For Te<150 km as suggested by McGovern et al [2002] and f=3, less than 20% of the geoid can be attributed to plume buoyancy. This percentage varies slightly for f=2 or 4. For plume buoyancy to contribute 20% of the geoid, plume buoyancy needs to be at depths >480 km. These results suggest that the Tharsis anomalies are largely caused by surface processes including volcanic construction. We will also discuss the results using all of the information contained in the amplitudes of each spherical harmonic coefficients.

Affiliated with

Also associated with

No associations

Rating

The origin of geoid and topography anomalies of the Tharsis rise does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The origin of geoid and topography anomalies of the Tharsis rise, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The origin of geoid and topography anomalies of the Tharsis rise will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-842914