The World’s Oldest Ocean Is Also The Biggest And The Deepest

The mighty Pacific Ocean is the largest and deepest of the world’s ocean basins, as well as the oldest, containing rocks that date back about 200 million years according to NOAA. The Pacific covers an area of 163 million square kilometers (63 million square miles) and is so large that it could contain all of the land on Earth. 

The world’s oceans are constantly changing as the tectonic plates in Earth’s crust move; this means that the Pacific Ocean is actually shrinking, as the Atlantic Ocean expands towards it. Within the Pacific is an area referred to as the "Ring of Fire" because of the high levels of volcanic and earthquake activity in these tectonic plates. 

As the oldest ocean in the world, it seems only right that it is also home to some very old seawater. According to research, the oldest water in the North Pacific has been trapped in a “shadow zone” deep under the surface for around 1,000 years. 

However, this is still pretty young in comparison to the oldest water in the world. A remnant from the North Atlantic Sea, this ancient H₂O was found under the Chesapeake Bay in an impact crater that was formed 35 million years ago. The water is thought by scientists to be between 100 and 145 million years old and has always been there, but was released by the impact of the asteroid and then trapped underneath. The water is so old that it has twice the salinity of modern seawater.

Older still is a tiny piece of the world's oceanic crust that lies undisturbed in the Mediterranean Sea. Thought to be around 340 million years old, it was formed when hot molten rock called magma welled up and then cooled. As it cooled at the mid-ocean ridge, the minerals in the magma became magnetized, allowing researchers to find the area with their magnetic sensing equipment. 

If all this talk of old water has wet your whistle, check out the oldest lake and the oldest river too.