Volcano F is the origin of 'floating stones': Stones do not float in water—this is a truism. But there is hardly a rule without exception. In fact, some volcanic eruptions produce a very porous type of rock with a density so low that it does float:… https://t.co/mFeUfD4vLz pic.twitter.com/jM0RdX4QRM

— (electro) Magnetic Universe (@NewsRounders) December 9, 2019