A bit longer than 250 million years is when we had the Great Dying, the Permian–Triassic extinction event, when up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct. A mere 65 million years ago saw the extinction of the dinosaurs and the dawn of the Cainozoic Era. From a screenshot of this YouTube, this is how the continents were placed around the globe:
India was on its way to slam into Asia, Eurasia had not yet formed and South America had split off from Africa.
This YouTube shows the shape of things in 100 million years time:
A bit of a mess, really.
Of course, the temperature and the shape of the ocean basins will determine how much land is showing.
A recent New Scientist article by Stephen Battersby (pay-walled) plotted possible futures out to 250 and 300 million years. Here’s one for 300 million:
And another for 250 million:
The money seems to be on a new supercontinent, probably to the north, with or without Antarctica. If you had an ice sheet on both poles it would make a difference to sea levels and climate.
The truth, however, is that beyond about 50 million years it is basically guesswork.
There are three main functions going on. Firstly, plates can slam into each other as with India and Asia. Secondly, you can have mid-ocean upwellings. Thirdly you have subduction zones, where one plate slides underneath the other.
You can see the active areas in this map of earthquakes from 1963 to 1998:
The major uncertainty is that scientists have no idea at all how new subduction zones form. They come from deep inside the earth’s surface, and are may millions of years in the making.
I’ve been intrigued by the Andes Mountains, where the 65 million years map shows the intrusion of the ocean along the west coast. Research a few years ago indicates that the Andes only started to rise 30 million years ago and was near full height 14 million years ago. Until then the Andes were thought to be younger, about 14 to 10 million years ago.
An intriguing factoid is that Ecuador’s Mt Chimborazo at 6,263m is actually the furthest point from the earth’s surface to its core.
James Hansen in his Iowa Testimony in 2007 explains how continental shifts and the upwelling of mountains affect the climate over long periods. Here is a rough picture of continental drift:
Here is how the temperature changed in the last 65 million years:
It changes very slowly with evolutionary processes able to respond. Something very different is happening now, with the sixth great extinction well under way.
250 million years would be an extraordinarily long time for a species like Homo Sapiens to survive. The realistic prospect is that nature will survive the plague-like infestation of this topline predator and destroyer of habitats like no other, and return to a gentler process where species continue to evolve and prosper. It may be a question of what damage we do on the way out.
Or will we learn to align with the underlying processes of change?
Nature’s big brain experiment is on the line.