The Pacific Ocean's days are numbered, according to a new supercomputer simulation of Earth's ever-drifting tectonic plates.

The good news? Our planet's oldest ocean still has another 300 million years to go. If the Pacific gets lucky, it might even celebrate its billionth birthday before finally trickling out of existence.

But researchers at Curtin University in Australia think the ocean is likely to be swallowed up before that.

In its final years of life, the Pacific will hardly resemble the vast expanse of blue it does today. Every year, the ocean shrinks a few centimeters, as it's been doing since it was a superocean surrounding the last supercontinent of Pangea.

The ancient ocean is home to numerous subduction zones; places tectonic plates collide and ride over the top of one other. Colloquially known in the Pacific as the 'Ring of Fire', these sites work almost like bath tub drains for the ocean floor.

Each year, a few centimeters of the Pacific plate slips under the Eurasian plate and the Indo-Australian plate, collapsing the distance between North America, Asia and Australia.

Not all scientists agree on what the next supercontinent will look like or how it will form, but in many simulations, the Pacific Ocean is doomed.

While some studies suggest the Atlantic Ocean, which is expanding today, might start to shrink in the future, thereby creating a supercontinent ringed by a super Pacific ocean, researchers at Curtin University disagree.

Instead of a second Pangaea-like continent (aka Pangaea Proxima) forming, they argue the world is headed for a supercontinent in which North America collides with Asia, dubbed Amasia.

Poor Australia gets left out of this 'cute couple' name, but in 4D geodynamic models, the Southern Hemisphere continent seems to play an important role in plugging up what's left of the Pacific.

The recent simulations from researchers in Australia are based on realistic plate and mantle parameters from the present and the past, which were then used by a supercomputer to predict the future.

"Over the past two billion years, Earth's continents have collided together to form a supercontinent every 600 million years, known as the supercontinent cycle," says Earth scientist and lead author, Chuan Huang.

"By simulating how the Earth's tectonic plates are expected to evolve using a supercomputer, we were able to show that in less than 300 million years' time it is likely to be the Pacific Ocean that will close, allowing for the formation of Amasia, debunking some previous scientific theories."

Contrary to some other supercontinent simulations, this new one suggests the Pacific Ocean, and not the Atlantic Ocean or Caribbean Sea, will be destroyed when Amasia forms.

In the current model, Amasia comes about when the Pacific closes due to the weakening of the upper layer of the ocean's crust.

"Earth as we know it will be drastically different when Amasia forms. The sea level is expected to be lower, and the vast interior of the supercontinent will be very arid with high daily temperature ranges," says geoscientist Zheng-Xiang Li.

But this is just the latest study in a long string of supercontinent simulations, all of which have tried to predict what our planet will look like in the future.

One more model is unlikely to end the debate, but this isn't the only one to predict the demise of the Pacific.

In a scenario where a supercontinent called Novopangaea forms, the Americas collide with Antarctica before crashing into Eurasia and Africa. This cuts off the Pacific in a different way but with similar results.

In another supercontinent scenario, called Aurica, both the Pacific and the Atlantic oceans close for good, and a new ocean basin arises in their stead.

Whatever the outcome, one thing is for sure: Earth and its oceans will never be the same again.

The study was published in the National Science Review.