Axial focusing of impact energy in the Earth's interior: A possible link to flood basalts and hotspots

Abstract

Seismological simulations show how energy from a large impact can be coupled to the interior of the Earth. The radially diverging shock wave generated by the impact decays to linearly elastic seismic waves. These waves reconverge (minus attenuation) along the axis of symmetry between the impact and its antipode. The locations that experience the most strain cycles with the largest amplitudes will dissipate the most energy and have the largest increases in temperature at a given depth (for a given attenuation efficiency). We have shown that the locus of maximum energy deposition in the mantle lies along the impact-antipodal axis. Moreover, the most intense focusing is within the asthenosphere at the antipode, over the range of depths where mechanical energy is most readily converted to heat. We suggest that if large impacts on the Earth leave geological evidence anywhere other than the impact site itself, it will be at the antipode. Strong axial focusing also occurs directly beneath the impact site and should be considered in models of impact-induced volcanism.

Impact induced melting and the development of large igneous provinces

“…In conclusion, we can only agree with the view of Boslough et al [11], who stated 'the impactproduced £ood basalt hypothesis is attractive because it is potentially testable on the basis of predictions of features that have not yet been discovered...unlike current plume models for £ood basalts and hotspots'. To resolve this issue fully, further ¢eld work (e.g.…”

“…Examples of such suggestions include the Bushveld Complex [4], the Deccan Traps [5,6], the breakup of tectonic plates [7,8], and the formation of oceanic plateaus [9,10] and continental £ood basalts [11,12]. These suggestions have usually been rejected on the grounds that an impact model is less plausible than the widely accepted plume model [13].…”

Triggering of the largest Deccan eruptions by the Chicxulub impact

“…The kinetic energy of the Chicxulub impact has been estimated at ~3 × 10 23 Joules (Boslough et al, 1996). Estimates for the effi ciency of conversion of impact energy into seismic waves as doi:10.1130/B31167.1 Geological Society of America Bulletin, published online on 30 April 2015 range from 10 −2 to 10 −5 (Schultz and Gault, 1974;Shishkin, 2007), implying effective moment magnitudes for Chicxulub in the range M w ~9-11, although such extrapolations depend upon the seismic frequency.…”

Evolution and Geological Significance of Larger Benthic Foraminifera

“…This might have happened, as explained in Chapter 3, as a response to an impact at the Triassic-Jurassic boundary (e.g. Boslough et al, 1996), which in turn might have triggered the eruption of a large igneous flood basalt province (e.g. Jones et al, 2005).…”