Wilson. The entire cycle seems to take about 500 million years, and there is no reason to believe that plate movement in the near (and far) future will alter this trend. The last supercontinent formation, Pangea, occurred some 300 million years ago, allowing a rough prediction that the next will occur in about 200 million years.

By about 100 million years from now, the continents will have reached their maximum separation and begin to coalesce. By 150 million years from now, the Atlantic will have become far smaller. Subduction will continue along the entire eastern seaboard of both North and South America as the Atlantic Ocean floor is subducted beneath the coastline along gigantic, linear subduction zones. This process will, in turn, create a series of high mountains along the eastern coastlines of those two continents. The Pacific Ocean will increase in size as the continents all begin a mad rush at mutual collision.

By 250 million years into the future, the process of continental amalgamation will have been completed. Europe, Africa, North and South America, and Asia will have formed the supercontinent; however, Antarctica and Australia will not be amalgamated. A curious aspect of this projection is the existence of a large, central equatorial sea. Because of the presence of subduction zones virtually encircling this giant supercontinent, a wall of mountains will enclose much of the land surface, walling off the interiors of the continent, just as the Andes, Sierra Nevada, Cascade, and Coast Range mountains—all high mountains with active volcanism—wall off the interiors of the western parts of North and South America.

But like the last time, this supercontinent will not last. When it breaks apart, it may be that Earth will once again experience a major drop in oxygen, perhaps the equivalent of the Permian mass extinction.

FUTURE WORK

It will be up to scientists to see how many of the new hypotheses offered in this radical revision of Earth’s history are accepted. If even a few are ultimately accepted, it will mean that we will have to revise our understanding of the whys in the history of life. If oxygen has varied



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