Exploring the World's Largest and Deepest Ocean, Also the Oldest.
The Pacific Ocean is the oldest, largest, and deepest ocean in the world, containing rocks that date back about 200 million years. The Pacific is constantly changing as the tectonic plates in Earth’s crust move, causing it to shrink while the Atlantic expands towards it. The oldest seawater in the North Pacific has been trapped in a “shadow zone” deep under the surface for around 1,000 years, while the oldest water in the world is thought to be between 100 and 145 million years old and has twice the salinity of modern seawater.