Global distribution of volcanic centers and mountains on Io: Control by asthenospheric heating and implications for mountain formation

• Published in: Earth and planetary science letters Vol. 301; no. 1-2; pp. 22 - 30
• Main Authors: Kirchoff, Michelle R., McKinnon, William B., Schenk, Paul M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 03.01.2011
• Subjects: orogenesis; spherical harmonics; tectonics; thermoelastic stress; volcanism; orogenesis; spherical harmonics; thermoelastic stress; tectonics; Io; volcanism
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2010.11.018

Jupiter's moon Io possesses numerous tectonic mountains in addition to its ubiquitous volcanoes and volcanic features. Remarkably, a distinct global anticorrelation exists between the spatial distribution of mountains and volcanic centers on Io. This relationship indicates an explicit connection between volcanism and mountain formation, even though the mountains are tectonic in origin (predominantly upthrusted crustal blocks). Spherical harmonic analysis shows the distribution of mountains and volcanic centers have statistically significant power at degree 2; this result is especially striking for the volcanic center distribution, and directly implicates models of asthenospheric tidal heating. The latter predict enhanced heat flux along the equator in a degree-two pattern that matches observations. Mountain formation on Io appears to be a form of dominantly vertical tectonism unique in the modern Solar System: continual burial by widespread volcanism drives the crust inward, which leads to strong compression, and at discrete locations, mountains. Correlation coefficients between the volcanic and mountain distributions indicate statistically meaningful anticorrelation at low spectral degrees (l=1, 2, 4, and 6); the anticorrelation is especially significant between the longitudinal (sectorial) l=2 components when considered on their own. We compare this anticorrelation with published models that link volcano and mountain formation. While consistent in part with l=2 convection models, which predict such an anticorrelation (in principle), such low degree anticorrelations are also (if not more) compatible with mountain formation due to, or influenced by, thermal expansion of Io's crust, and deep compression and thrust faulting in regions of lower than average volcanic heat-piping. Positive correlations between mountain and volcanic center distributions at high spectral degree may reflect structural links between a good fraction of mountain blocks and adjacent volcanic paterae, whereas the anticorrelation at low degree implies that most volcanic features (which are far more numerous overall) form independently of mountains. ► Spherical harmonic statistical analysis of Io’s volcano and mountain distributions. ► Strong degree-2 spectral power for both, with volcanic power at higher degrees less than random. ► Volcano distribution favors tidal heating models with compositionally distinct asthenosphere. ► Significant anticorrelation between mountains and volcanoes at low spectral degrees. ► Consistent with large compressional stresses and orogenesis in regions of reduced volcanism.