According to Genesis 1 at the beginning when God formed the Earth there was one land mass and one chaotic universal ocean (Genesis 1:2). The Creator separated the dry land from the waters, setting boundaries for both. The single land mass or supercontinent is called "Pangea" and the separation into the 5 continents - Africa, America, Asia, Europe and Oceania - took millions of years. The following video depicts what scientists believe our Earth will look like in 100 million years.
Related reading: Parsing Genesis 1; The Pillars of the Earth