Exploring the Oceans. Chapter 16. Chapter 13. Section 1 Earth’s Oceans. How Did the Oceans Form?. About 4.5 billion years ago, there were no oceans. Sometime before 4 billion years ago, water vapor in the atmosphere condensed and fell as rain.
Section1 Earth’s Oceans
Salinity varies in different parts of the ocean because of variations in evaporation, circulation, and freshwater inflow.