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Spatial distribution of volcanoes on Io: implications for tidal heating and magma ascent

Hamilton, Christopher W.; Beggan, Ciaran D.; Still, Susanne; Beuthe, Michael; Lopes, Rosaly M.C.; Williams, David A.; Radebaugh, Jani; Wright, William. 2013 Spatial distribution of volcanoes on Io: implications for tidal heating and magma ascent. Earth & Planetary Science Letters, 361. 272-286. 10.1016/j.epsl.2012.10.032

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Abstract/Summary

Extreme volcanism on Io results from tidal heating, but its tidal dissipation mechanisms and magma ascent processes are poorly constrained. Here we analyze the distribution of volcanic hotspots and paterae identified within the first 1:15,000,000-scale global geologic map of Io to characterize their patterns of spatial organization. Ionian hotspots correspond to the locations of observed positive thermal anomalies, whereas paterae are caldera-like volcano-tectonic depressions that record locations of volcanic activity over a longer period of geologic time. Some (~20%) of patera floor units are associated with active hotspots, but the majority appear to be extinct or dormant at the time of observation. Volcano distributions are useful for testing interior models of Io because the relative strength of tidal heating in the asthenosphere and deep-mantle greatly affect expected patterns of surface heat flux. We examine the distribution of volcanic centers using nearest neighbor (NN) statistics and distance-based clustering. Nearest neighbor analysis reveals hotspots to be globally random, but closer to the equator, they are uniform (i.e., more widely spaced than a random model would predict). This implies that magma scavenging and/or tectonic controls around active volcanic systems in near-equatorial region may drive hotspots apart. Globally, vigorous mantle convection and/or deep-mantle heating may reduce surface heat flux variations and promote randomness within the overall hotspot distribution. In contrast to the hotspots, NN patera floor units are globally clustered, but randomly distributed near the equator. This implies that on a global-scale patera floor units tend to concentrate close to one another, but in the most densely populated near-equatorial region, overprinting may randomize their distribution over time. Distance-based clustering results support a dominant role for asthenospheric heating within Io, but show a 30–60° eastward offset in volcano concentrations from predicted locations of maximum surface heat flux along the tidal axis. This offset may imply faster than synchronous rotation, a role for lateral advection of magma within Io’s interior prior to its eruption, state of stress controls on the locations of magma ascent, and/or a missing component in existing tidal dissipation models, such as the effects of fluid tides 48 generated within a globally extensive magma ocean.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.epsl.2012.10.032
ISSN: 0012-821X
NORA Subject Terms: Space Sciences
Date made live: 17 Jun 2013 11:51 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/502289

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