As Narf said, that would be hiding it, with similar basic objections to throwing it into the depths of the ocean.  In a subsequent eruption I would imagine the Ring would be blown out in a lump of pumice to be found by who knows what, but it would probably have found its way back to Sauron in any event.  The Council of Elrond decided they had to look to the safety of future ages, (the reason also for not choosing the sea option), so this would be labelled a 'Bad Idea' in the long run.

Secondly there is a more practical objection, in that Mount Doom is the only volcano on the map of Middle-earth.  You can imagine there were others, far to the east or south, but getting there would mean traveling through regions mainly inhabited by Sauron's allies, and if they did manage to avoid them, by the time they had accomplished their mission, Sauron would have won the war back home anyway.