The document discusses the origin of ocean basins. It states that oceans formed around 3.8 billion years ago through three phases as the Earth cooled. Initially, there was only water vapor in the atmosphere that was too hot for liquid water. Condensation eventually led to rain and the accumulation of water on the surface to form oceans. The continents were once united in a supercontinent called Pangaea with a single global ocean, but plate tectonics have since caused the continents to move to their current positions and form the five major oceans that exist today.