The Unknown Zone: Islands that have Disappeared

Tonight's Unknown Zone features a little known phenomena where known islands have disappeared without a trace.  From Bermeja, Mexico to Hy-Brazil west of Ireland islands have been mapped with a know history only to have disappeared for no apparent reason.
These islands can't even be found under the ocean where they once stood. Can people places and things just vanish from the Earth?  Avalon, the Anasazi, the Maya and now islands join the mythic ranks of the unknown.   Judy Sellins and Dave Turco will shed light on the very odd mystery