The Bungie Credit Terminals are secret terminals placed within the various installments of the Marathon Trilogy, usually on the final level of the solo scenario. They are not considered part of the plot, but are messages from the game designers at Bungie Software.
After raising the lava, go to the beginning of the level. Go downstairs and get x3 shields (unless you already have them). Go down the lava stairs and swim up to the room where you broke the lava control circuits. Turn directly to the right... there should be circuits there. Break the circuits to open a door to the Bungie Credit room jump pad. Now go down the hallway into the big area. Swim into the middle part and go to the right to see the opened aforementioned door. Drift down the hole and there should be an opening. Go in the opening and swim up to a hallway. There is a x3 recharger at the end of it. Recharge and find the jump pad to the Bungie Credit room. Note: you must move immediately when in the room, or you will be teleported to the final room.