William B. McKinnon
Michael T. Bland
2016
<p>Jupiter’s volcanic moon Io possesses some of the highest relief in the Solar System: massive, isolated mountain blocks that tower up to 17<span class="mb"> </span>km above the surrounding plains. These mountains are likely to result from pervasive compressive stresses induced by subsidence of the surface beneath the near-continual emplacement of volcanic material. The stress state that results from subsidence and warming of Io’s lithosphere has been investigated in detail<sup><a id="ref-link-2" title="Turtle, E. P. et al. Mountains on Io: high-resolution Galileo observations, initial interpretations, and formation models. J. Geophys. Res. 106, 33175-33200 (2001)." href="http://www.nature.com/ngeo/journal/v9/n6/full/ngeo2711.html#ref1">1</a>, <a id="ref-link-3" title="McKinnon, W. B., Schenk, P. M. & Dombard, A. J. Chaos on Io: a model for formation of mountain blocks by crustal heating, melting, and tilting. Geology 29, 103-106 (2001)." href="http://www.nature.com/ngeo/journal/v9/n6/full/ngeo2711.html#ref2">2</a>, <a id="ref-link-4" title="Jaeger, W. L. et al. Orogenic tectonism on Io. J. Geophys. Res. 108, 5093 (2003)." href="http://www.nature.com/ngeo/journal/v9/n6/full/ngeo2711.html#ref3">3</a>, <a id="ref-link-5" title="Kirchoff, M. R. & McKinnon, W. B. Formation of mountains on Io: variable volcanism and thermal stresses. Icarus 201, 598-614 (2009)." href="http://www.nature.com/ngeo/journal/v9/n6/full/ngeo2711.html#ref4">4</a></sup>; however, the mechanism of orogenesis itself and its effect on regional tectonism and volcanism has not been firmly established. Here we present viscoelastic–plastic finite element simulations demonstrating that Io’s mountains form along deep-seated thrust faults that initiate at the base of the lithosphere and propagate upward. We show that faulting fundamentally alters the stress state of Io’s lithosphere by relieving the large volcanism-induced subsidence stresses. Notably, in the upper portion of the lithosphere, stresses become tensile (near-zero differential stress). A number of processes are therefore altered post-faulting, including magma transport through the lithosphere, interactions with tidal stresses and potentially the localization of mountain formation by thermoelastic stresses. We conclude that Io’s mountains form by a unique orogenic mechanism, compared with tectonic processes operating elsewhere in the Solar System.</p>
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10.1038/ngeo2711
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Nature Pub. Group
Mountain building on Io driven by deep faulting
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