Origin of the oceans
Topic: Origin and Evolution of the Earth and the Solar System · NCERT: Class 11, Ch 2 "The Origin and Evolution of the Earth"
Meaning
The oceans formed as the Earth cooled. Water vapour released by degassing condensed into rain, and the rain dissolved carbon dioxide from the air. As the Earth cooled further, more rain fell and filled low-lying basins (depressions). The oceans formed within 500 million years of the Earth's birth, so they are about 4,000 million years old. Life later began in these oceans.
Example
The water in the Bay of Bengal comes from this ancient rainfall. The sea floor under it, however, is much younger, because ocean floors keep forming and being destroyed through plate movement.
Don't confuse with
- Age of the ocean basins: the water is about 4,000 million years old, but today's ocean floors are much younger. The basins changed shape again after Pangaea broke up about 200 million years ago.