Lava is strong yet it's slow moving if it hits something it melts it down, BTW steel melts at 1783.15 kelvin (2750F), Magma (Lava) temperatures range depending on there location but the range is anywhere from 1173.15 kelvin(1652F) to 1773.15 kelvin(2732F); man of steel would have died.
But I believe the Son Goku and Roshi would have been more skilled in Lava release than the 4th Mizu, but again that jutsu is actually seems slower than most if someone is hit there in for some trouble.
Now what I believe is the worst Natural Disaster is Hurricanes, simply they utilize almost every element Heavy Winds, Tornadoes, Lightning, Floods, Hail, and from lightning; fire.