The Norfair stage is a basic tri-level stage. Theres lava at the bottom on many occassions that can prevent you from falling down to your doom, however it does damage you.
Lava is a very common thing in this stage as many times there will be lava attacks. The lava may come from below and concompass the bottom levels of the stage, forcing you to get to the top. The lava has also been known to come in from the sides, pushing you to the other side else you'll get damaged. Sometimes a lava pume will be sent through the stage from behind and on the odd occassion, a massive wave will come and encompass the entire level, requiring you to get to the one special bunker that arrives on the stage