Earth’s current largest ocean, the Pacific, covers more than 30% of the planet’s surface, stretching 19,000 kilometers at its widest point between Columbia and the Malay Peninsula. However, this represents only the remnants of the largest ocean in Earth’s history.
The largest ocean ever to exist would be Panthalassa, a world-spanning sea that surrounded the supercontinent Pangea from about 300 million to 200 million years ago, Brendan Murphy, a geology professor at St. Francis Xavier University, told Live Science.
“The biggest ocean usually happens when supercontinents form, because if you only have one large supercontinent, then you’ve only got one ocean that exists around it,” said Murphy.
That has likely happened multiple times, said Murphy, buy all those single Earth’s oceans would have been comparable in size. The most recent supercontinent was Pangea, in which today’s continents fit together like a puzzle. Another supercontinent, Rodinia, combined Earth’s landmasses in a different configuration roughly 650 million years ago.
Panthalassa would have increased the Pacific’s width by another 3,000 kilometers. By surface area, Panthalassa dwarfed the Pacific, covering nearly 70% of the Earth’s surface, or nearly 360 million square kilometers.
Pangea broke up due to the opening of the Atlantic Ocean with its remnants becoming the Pacific.
About 150 million years after Earth formed, it had no continents, so an unbroken sea covered the planet.
The Pacific has been the world’s largest ocean since the demise of Pangea around 200 million years ago. However, if current projections of tectonic plate movements hold true, Australia will split the Pacific in two over the next 70 million years.