I was using gascraft gas for cheep power till it leaked and got out of control it normally de-spawns on its own in open air but it seams that do to some plugin on the server it dose not de-spawn it just makes more gas as it spreads this gas explodes 5 as bad a TnT and torches in near by mines have added to it expanding because they light parts of the cloud as it spreads. the gas blocks can't be broken with a pick in game and you can't remove it with a bucket. I got a mod to try and help but she could not do any more then I could to stop it. I fear lightning may light the gas and it go off like a nuke.
I hope it can be fixed and I think gascraft should be banned because of this problem at lest I did not use nether plasma that would have set the sky on fire.
I removed all Hydrogen blocks (2097) in a 75 block radius from your base and it seems to have stopped spreading now, if it reoccurs as bad as it did then please reply to this thread and we'll further look into it.