Volcano distribution

Volcanoes on Io (and for that matter, the mountains too) do not appear to follow a distinct global pattern, suggesting that any surface expression of internal dynamics (convection) is subtle. Active hot spots appear to be randomly distributed (LopesGautier et al., 1999). The distribution of mountains and paterae (including those which have not been observed to be active) is, however, not random, as both types of features are concentrated toward lower latitudes and follow a bimodal distribution with longitude (based on available imagery). The greatest frequency of mountains occurs in two large antipodal regions near the equator at about 65° and 265° (Schenk et al., 2001). In contrast, the volcanic patera follow a similar distribution but 90° out of phase with that of the mountains (Radebaugh et al., 2001). The bimodal distribution pattern for paterae and other volcanic centers matches the expected pattern of heat flow from asthenospheric tidal heating (Ross et al., 1990) and the pattern of internal convection within the mantle predicted from simulations (Tackley et al., 2001). Jaeger et al. (2003) found that 41% of tectonically derived mountains are associated with paterae, and suggested that orogenic faults on Io act as conduits for magma ascent, fueling patera formation near mountains (see Chapter 6).

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