In the last 2 billion years of Earth’s geological history, continents have been regularly approaching and moving away from each other in cycles of approximately 600 million years. Therefore, the reunification of the continents in the future seems inevitable. But geologists have long debated whether this merger will happen when the west coast of the Americas joins with Asia, or if the east coast rejoins with Europe and Africa. A new study says fundamental changes are taking place deep inside the Earth, so only the first of these possibilities is possible.
The merging of continents causes most of the Earth, with the exception of small islands, to be covered by a single huge ocean. This single large ocean that existed during the Pangea era, the last supercontinent, calls it Panthalassa. During the separation of the continents, the number of oceans on Earth also increases, and the ones between the separated land masses are called the inner ocean, and the side where the land masses advance is called the outer ocean. The Atlantic and Indian Oceans are the remnants of the ancient inland seas, while the Pacific is defined as the outer ocean as the remaining part of the Panthalassa.
At least, Curtin University Professor Zheng-Xiang Li and co-authors say in the article published in the National Science Review, Earth has now entered a phase where only the outer oceans can close. So, the disappearance of the Pacific seems inevitable.
The Atlantic Ocean is currently growing at a rate of a few centimeters per year, and the Pacific is shrinking at a similar rate. So by expanding this calculation, it’s easy to determine when the region, which is now the world’s largest ocean basin, will close. Geologists have done this before and named the supercontinent that will form as Amasia (Amasya). Li said it will take 280 million years for the remnants of Pangea to coalesce at the current rate. However, it has also been observed in the past that these currents changed direction and closed the inner ocean again.
That change is no longer possible, the article says. The authors’ modeling suggests that continental movements are largely dependent on the strength of the oceanic crust. Only when the crust is strong can the continents change direction and come together over young inland oceans.
As the Earth’s crust cooled, the oceanic crust that formed on it began to thin and weaken. 540 million years ago, Earth’s temperature cooled enough to no longer allow such reversals to occur, Li and co-authors found. That’s why Amasia and all future supercontinents will emerge from the outer ocean…
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