RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 7, ES6004, doi:10.2205/2005ES000193, 2005
On the estimation of elastic stresses in the mantle at the time moment of a large meteorite fallS. M. MolodenskyInstitute of Physics of the Earth, Russian Academy of Science, Moscow, Russia ContentsAbstract[1] Simple relations are obtained for estimating stresses in the mantle at the time moment of a large meteorite fall from values of the velocity and mass of the meteorite and the sizes of its crater. It is shown that the fall of the Chicxulub meteorite, the largest over the last 100 Myr, produced stresses of the order of 0.1-1 MPa. Backmatter[2] Jones et al., [2002] proposed a hypothesis according to which the fall of a large meteorite (such as the Chicxulub meteorite 10-16 km in diameter, which fell 65 Myr ago at a velocity of about 11 km s -1 and produced a crater 180-300 km in size) can activate convection in the lower mantle and provoke the formation of plumes in the D'' layer. An attempt to estimate the order of magnitude of elastic stresses arising at the time moments of such events is made in the given paper.[3] The main uncertainty involved in the estimation of elastic stresses is related to the question of which part of the kinetic energy of a meteorite is converted into heat and which part, into the energy of seismic vibrations. It is natural to divide the fall process into two phases: (1) the phase of inelastic impact (accompanied by the fracture of material in a region comparable in size with the crater) and (2) the phase of elastic interaction of the resulting fragments with the mantle. [4] As follows from the law of conservation of momentum, the average velocity of fragments in the first phase is determined by the relation
[5] The phase of elastic interaction of fragments with the mantle outside the crater can be described by the elastic energy balance
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[6] In accordance with the equation of the energy balance in the second phase of the process, the stresses in the wavefront region efr are determined by the relation
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![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() [7] This value is about an order of magnitude smaller than the tectonic stresses developing in the crust and upper mantle before an earthquake. ReferencesJones, A. P., G. D. Price, P. DeCarli, N. Price, and C. Hayhurst (2001), Modelling impact decompression melting: a possible trigger for impact induced volcanism and mantle hotspots, in: Abstracts, ESF Workshop on Impact Markers in the Stratigraphic Record, Eds.: F. Martinez-Ruiz, M. Ortega-Huertas, I. Palomo, p. 57, Universidad de Granada, Granada.
Received 12 November 2005; revised 21 November 2005; accepted 1 December 2005; published 14 December 2005. Keywords: stresses in the mantle, geodynamics. Index Terms: 8164 Tectonophysics: Stresses: crust and lithosphere; 8168 Tectonophysics: Stresses: general; 1236 Geodesy and Gravity: Rheology of the lithosphere and mantle. ![]() Citation: 2005), On the estimation of elastic stresses in the mantle at the time moment of a large meteorite fall, Russ. J. Earth Sci., 7, ES6004, doi:10.2205/2005ES000193. (Copyright 2005 by the Russian Journal of Earth SciencesPowered by TeXWeb (Win32, v.2.0). |