You hurl molten lava at the target, dealing X Fire damage. If your Flame Shock is on the target, Lava Burst will deal a critical strike.
Lava Burst is an Elemental Shaman's highest hitting spell, due to it having a 100% crit chance if the [Flame Shock] DoT is on the enemy. It is on a 8sec cooldown, thus causing shaman dps rotations to be governed by cooldowns and priorities.
1012 - 1290
1192 - 1518
If Flame Shock is applied for the first time while Lava burst is traveling to the enemy (in other words, after Lava Burst has been cast), the 100% critical strike chance will not apply.
The Flame Shock DoT only has to be active upon completion of casting Lava Burst. If the DoT wears off while the Lava Burst projectile is traveling, it will still crit.
PvP - Lava burst and [Chain Lightning], which has no traveling time, if cast in succession will generally hit at the same time for spike damage.
Enhancement shamans do not normally use this ability (unless the shaman is out of melee range and unable to close in, for example). The main issue is that it has a cast time and is not on Maelstrom Weapon. Because of that, Lava Burst stops auto attacks and pauses the swing timer, so it is best to use Chain Lightning or Lightning Bolt (both of which benefit from Maelstrom Weapon haste) instead.
3.2.2[Lava Burst]: This ability no longer ever consumes a Flame Shock debuff off of the target.