Tech & Science

When Earth's Supercontinent Pangaea Was Torn Apart 130 Million Years Ago, the Planet Warmed Up

An aerial view of the East African Rift System, the largest rift on Earth today. Brune, Nasa WorldWind

No one would have thought continents tearing themselves apart would be calm, but scientists have just uncovered evidence that the process has consequences far above the surface of the Earth as well. That's according to a paper published Monday in the journal Nature Geoscience.

In the paper, a team of German and Australian scientists tallied up how much land was being torn apart over time and compare the extent of this activity, called rifting, to carbon dioxide levels in the atmosphere. They found that it makes a much larger carbon contribution than scientists had previously expected, especially compared with a showier source of carbon from plate movements, at volcanoes.

While we tend to be focused on the carbon cycle of compounds moving between the atmosphere, the ocean and the upper layers of the Earth's surface, there's a whole lot more carbon that is typically locked safely away in the heart of the planet. But as continents literally tear themselves apart, they can free some of this carbon, leading to a spike in global levels.

"Rift systems develop by tectonic stretching of the continental crust, which may lead to breakup of entire plates," lead author Sascha Brune, a geoscientist at the GFZ German Research Centre for Geosciences, said in a press release.

Right now, the largest such rift system is in East Africa, where the Earth is tearing apart over a network of almost 4,000 miles. That sounds dramatic, but it's small potatoes compared with the rift activity about 130 million years ago. Then, about 25,000 miles' worth of rifts tore apart the supercontinent Pangaea, a massive breakup that included snapping India and Australia off Antarctica and other gigantic cracks spider-webbing across the planet. The scientists also looked at a second spike in rifting activity that took place about 55 million years ago.

In each case, they calculated the amount of carbon production they expected based on how quickly modern rifts produce the stuff. Then they compared those peaks with records of carbon dioxide in the atmosphere and found that the two rates matched up pretty well.

There may well be more discoveries to be made about the unexpected impact of plate tectonics, since scientists began to accept the theory only about five decades ago. That happened in spite of the theory's proposal in the 1910s, by scientist Alfred Wegener.

The authors of the new paper are quick to add that today's rift systems aren't responsible for all that much carbon dioxide production, at least not next to human activities. We can't blame today's climate change on the Earth splitting open under our feet.

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