More than likely I did not use the correct terms to describe this stuff, but...

You can't have rebound peaks forming in cooled lava - but you can have them forming in cooled "pyroclastic" mud - essentially the CO2/H2O/rock suspension which forms from your clathrates under gravitational pressure at depth -

Several years back, one of the world's leading meteorite experts, Mr. Michael Casper, allowed me to closely examine a large chunk of Mars, a shergottite if I recall correctly. The rock looked like a piece of fine grained granite, but amazingly felt as though it had the density of styrofoam -

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