Giant impacts and the initiation of plate tectonics on terrestrial planets



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Ruiz Pérez, Javier (2011) Giant impacts and the initiation of plate tectonics on terrestrial planets. Planetary and Space Science , 59 . pp. 749-753. ISSN ISSN: 0032-0633

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Earth is the only terrestrial planet with present-day lithosphere recycling through plate tectonics.
However, theoretical models of mantle convection based on general considerations find that all the
terrestrial planets should be operating in the stagnant lid regime, in which the planets are one-plated
and there is no lithosphere recycling. The stagnant lid regime is a consequence of the strong viscosity
contrast across the convective layer, and therefore the upper lid (roughly equivalent to the lithosphere)
must be sufficiently weakened in order to be mobilized. Here I propose that giant impacts could have
provided the upper layer weakening required for surface recycling, and hence for plate tectonics, to
initiate on the early Earth. Additionally, giant impacts originated lithosphere thickness and density
differences, which might contribute to the initiation of subduction. Impacts are more energetic for
Earth than for Mars, which could explain the likely early existence of plate tectonics on the Earth
whereas Mars never had lithosphere recycling. On the other hand, convection on Mercury and the
Moon might be sluggish or even inexistent, implying a reduced influence of giant impacts on their
internal dynamics, whereas there is no record of the earliest geological history of Venus, which
obscures any discussion on the influence of giant impacts on their internal dynamics.

Item Type:Article
Uncontrolled Keywords:Plate tectonics; Mantle convection; Giant impacts; Lithosphere; Stagnant lid
Subjects:Sciences > Geology > Geodynamics
ID Code:16857
Deposited On:24 Oct 2012 09:27
Last Modified:24 Oct 2012 09:27

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