Actually, it sounds like what happened after the last time the continents split................

One way to understand Middle-earth's place in Tolkien's complex system is to see his whole creation as a series of worlds within worlds. As the outer layer is the whole universe itself, called by Tolkien "Eä". Within Eä are many mysterious and unknown worlds, but the events of his stories take place in the world called "Arda". Arda is what we would call Earth, called by Tolkien "Imbar" or "Ambar" (meaning 'the Habitation') and the sun, moon and stars which revolve around it. Within Arda are the continents of Aman and Middle-earth (which was actually two or even more continents), which are separated from each other by the Great SeaBelegaer (analogous to the Atlantic Ocean). Within his stories, Tolkien translated the name "Middle-earth" as Endor (or sometimes Endórë) and Ennor in the Elvish languages Quenya and Sindarin respectively, sometimes referring only to the continent that the stories take place on, with another southern continent called the Dark Land.

The western continent, Aman, was the home of the Valar and the Elves called the Eldar. An uninhabited Eastern continent is also mentioned, but does not figure in the stories. The island of Númenor lay in Belegaer between Aman and Middle-earth, but was later drowned. In later ages Aman was also removed by the creator Eru Ilúvatar from Arda completely to prevent Men from trying to reach it.