Here's some concept art I made a couple years ago.
Edit: here's the description I posted on UO when I first invented it:
The eastern side of the island is continually rising (which produced the mountain peak), while the western slope is sinking. The resulting rift creates the outlet for the magma, which constantly flows down the western slope. On the way it becomes relatively cool and forms a layer of new rock. When the lava meets the ocean, it cools completely, releasing its heat in the form of steam, which produces a locally high humidity. Because of the updraft produced by the open lava flow, the water-laden air is drawn back up the side of the mountain, where the air cools and produces cloud, and rains on the eastern slope. Also on the eastern slope is a spring, which is produced by warm water flowing through an underground tunnel. The rainwater cools the spring water, and they flow down together on the eastern slope back into the ocean. The resulting water erosion keeps the height of the eastern slope at a constant level, just as the cooling lava keeps the height of the western slope from falling. The result is a perfect balance, while channeling usable energy from the earth's inner heat to the surface. The d'ni colony in the center of the island uses both the lava flow and the river as sources of energy, especially together.
Guild of Writers
one thing though, I've seen with alot of people, that they want to create ages the D'ni went to... we can't do this... we're sposed to be writers, not "Old D'ni age finders" we're not the DRC in other words. perhaps cyan will give us permission to use D'ni names in the ages... but... other than the thing about the D'ni, this looks like a reely kewl age 
