I have seen blue fire how hot is that, and what causes fire to turn blue. I also strangely noticed blue lava a little bit, I was near a volcano, why was the lava blue? What caused this? I saw blue lava and threw sometime like paper in and it burned faster not only that the small amount of lava made me thirsty so I left.
Generally speaking, Lava tends to be between about 2000 & 2200 degrees F. but it is hotter when it's under more pressure and under greater depth. Lava can be up to about 2900 degrees and even higher but when it includes gases that are explosive and under pressure and great depth, it can get to be a higher temperature. Now when it gets near the surface, that pressure is being relieved and so the temperature is going down again but at the same time, it's burning the gases within the material and combining with the oxygen in our atmosphere which means that the temperature is rising once again.....so I'd imagine that when you're seeing a blue flame, you're seeing natural gases which are burning at upwards of about 2800 degrees or higher, the lava isn't really blue it'self but the gas in the lava is and it appears that way......So I'd say that's a pretty good guess. I've been in the metalurgy business for quite awhile and I've had to deal with whats' called "slag"..which is a close facsimile to Lava....Slag is basically left over glass made from "air" coming in contact with melting metal in crucibles when you're using a flux material to help insulate the top of a portion of a pot full ( or crucible ) of metal before you pour a mold with the molten metal (or whatever you're doing with it) Lava is basically Slag too but with no metal in it....it's really neat to watch it melt and see the kind of flames different metals produce.......and the types of flames always indicate the types of gases released from the metals or the slag....or the types of metals are in the slag it'self.