The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § Vertical datum).
I think it might be called the "tail." I might be getting this mixed up with a comet, but I THINK(emphasis on think ^^') they're similar in that aspect?? Sorry if this didn't help.
