This is from Emily on twitter: "Kargel: Ammonia-water cryolava w/ methane, CO2 would make frothy, pumice-like deposits on Titan. Cool."
I'm not sure if this was referring to Sotra Facula, or from this other presentation: http://adsabs.harvard.edu/abs/2010AGUFM.P22A..02K
I just want to summmarise my three favourite reasons why the possibility of frothy, pumice-like deposits on Titan is really really
1/ Their formation would be a direct consequence of Titan's thick atmosphere. Bubbles formed in a liquid exposed to a vacuum would expand indefinitely and burst. Only bubbles 'erupted' under an atmospheric lid can stop expanding and remain in the liquid long enough for it to freeze (or set solid for some other reason).
2/ They could act as crack fillers. Imagine a system of crustal fissures repeatedly opened and closed by tidal flexing for example. At each opening the filler-foam pours in and so the crack cannot fully close again. This is a way to produce crustal extension, conceivably contributing over time to the building of Titan's compressive mountain chains unlike anything observed on other icy moons.
3/ They could float on liquid methane. This would greatly assist their mobility across the landscape. They could form piles of flotsam bulldozed around the surface by flash floods, perhaps helping to form the beach- and moraine-like features at the Huygens landing site, and they would be relatively easily moved by winds too over both land and sea.