Lava jars can be found in some levels. The timer on the jar counts down by one with every move. Lava jars can't be moved, but you can get rid of them by making matches near them or by using power-ups.

IMPORTANT: If you don't remove a jar before its timer reaches zero, the lava will spread and cool down. That lava can only be removed with power-ups.

Try to remove lava jars from the field before their timers reach zero, so you don't have to blow up cooled lava :)