Talk:Inactive Lava Zone/@comment-24573957-20150804023822/@comment-68.45.105.74-20150928211015

Water's boiling point isn't just 100 degrees C. It varies by pressure. At sufficient depth, water's boiling point can exceed rock's melting point, and the two will coexist. Yes, rock's melting point varies, too, but it varies at a different rate. I'm running numbers right now (thanks google for calculators) and I don't believe the inactive lava zone is actually that deep, but it is close.

All of this is very, very napkin math, if I'd even give it that much credit, but the underlying physics is true.