Antipodal Hotspots on Earth: Are Major Deep-Ocean Impacts the Cause?

Details Antipodal Hotspots on Earth: Are Major Deep-Ocean Impacts the Cause? Antipodal Hotspots on Earth: Are Major Deep-Ocean Impacts the Cause?

Feb 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003icbg.conf...27h&link_type=abstract

Impact Cratering: Bridging the Gap Between Modeling and Observations, p. 27

Physics

Volcanoes, Structural Basins, Plumes, Mars Volcanoes, Mars Surface, Impact, Ocean Bottom, Volcanology, Terrain, Symmetry, Statistical Analysis, Mercury (Planet), Core-Mantle Boundary, Angular Distribution, Statistical Distributions

Scientific paper

Hotspot volcanism on Earth is restricted to relatively small areas, on the order of 100 km in diameter, and is generally believed to result from narrow upwellings of hot mantle material called "plumes". At first glance, hotspots appear randomly distributed. General associations with geoid highs and divergent plate margins have been noted, and hotspots tend to occur in provinces separated by spotless areas. Matyska investigated angular symmetries of hotspot distributions, and showed that the highest maxima were obtained with 180 deg. rotations. Rampino and Caldeira also conducted a statistical analysis of large and small data sets and found that more hotspots occur as nearly antipodal pairs than would be expected from random distributions. The rise of antipodal plumes from the core-mantle boundary through a convecting mantle seems unlikely, but axial focusing of an impact's energy by the spherical Earth might underlie the antipodal pairing of hotspots. Such a focusing mechanism has been proposed to explain seismically disrupted terrains antipodal to major impact basins on the Moon and Mercury, and to have formed fractured crust on Mars opposite the Hellas basin-perhaps later exploited as a conduit for volcanism at Alba Patera. First-order problems with this model for Earth, however, include the expected low seismic efficiency of impacts and the lack of any volcanic features opposite large continental impact structures (e.g. Chicxulub).

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