Calderas on Titan: Implications for Cryovolcanism

Details Calderas on Titan: Implications for Cryovolcanism Calderas on Titan: Implications for Cryovolcanism

Dec 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.p13a0150m&link_type=abstract

American Geophysical Union, Fall Meeting 2006, abstract #P13A-0150

Other

5480 Volcanism (6063, 8148, 8450), 6207 Comparative Planetology, 6281 Titan, 8425 Effusive Volcanism, 8440 Calderas

Scientific paper

Cassini radar imagery obtained during the T16 (07/22/06) Titan fly-by reveals multiple probable volcanic calderas, some nested, at high latitudes (>70 N). We infer the presence of buoyant plumes from unknown depths that stall in the shallow crust (a few km depth) to form magma chambers. These would feed multiple cryovolcanic eruptions before chamber collapse and caldera formation. The concentration of calderas in this region, in comparison with other scenes, leads us to speculate that one or more massive hot spots under this region are feeding the plumes. Buoyant plume rise is only possible if the melt contains a substantial low-density non-water component, most likely ammonia and/or methanol, which also deflate the liquidus. If residence times were sufficiently long, pre- eruptive cooling and differentiation of cryomagmas within the shallow magma chambers would occur. Hence, relative to deeper-sourced activity, subsequent eruptions would be enriched in ammonia and/or methanol, and less prone to freezing during ascent. Individual eruptive volumes, most likely lava flows, would be small - orders of magnitude less than the calderas, based on comparison with the terrestrial planets - and difficult to resolve with Cassini Radar directly, although their presence might be possible to infer from topographic expression or textures resulting from multiple eruptive events. The T16 scene contrasts with the more voluminous cryovolcanic features revealed in the lower latitude Ta fly- by, including the 180-km-diameter dome-like Ganesa Macula, and several large flows. This contrast most likely reflects a difference in magma transport mode, perhaps echoing the difference between terrestrial shield- forming and flood basaltic volcanism. We propose that the larger features are the result of more massive eruptions sourced from greater depths; perhaps an ammonia-water ocean or mantle. Eruption temperatures would have been relatively high, and viscosities low, except where shear stresses and transport rates are low, in which case the non-Newtonian nature of water-rich cryovolcanic slurries may result in more topographically pronounced landforms.

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