Running down the center of the main continent on Fehnnia is a great rift valley, like the beginings of a yet to be flooded Atlantic ocean. Like the Atlantic basin, there is a great central fissure where the crust plates have split and new material wells up from deep within. Because the whole basin is several thousand meters below sea level, it has trapped all the heavy poisonious gasses from the various volcanic vents and is impassable on the surface. Only by flying over it all has the area been explored.