Researchers from the GFZ German Research Center for Geosciences in Potsdam have discovered that continental break-up — also known as rifting — may significantly increase atmospheric CO2 concentrations, a new study published in Nature Geoscience reports.
There are several factors that influence the amount of carbon dioxide in the atmosphere. While humans play a big role, the gases are affected by a wide range of geological and biological processes as well. This new look at rifting is another example of such processes.
Earth’s carbon distribution is highly unbalanced. In fact, just one-hundred-thousandth of the total CO2 on the planet is found in atmosphere, biosphere, and oceans. The rest is deep in the Earth. Even so, the two carbon stores are not isolated from each other. Rather, they go through a constant exchange over millions of years.
In the past, researchers postulated the exchange occurs with both tectonic plates, which take large amounts of carbon with them into the deep mantle, and volcanism, which releases CO2 up from the Earth and into the atmosphere. However, the team in the new study reports that might not be true.
The researchers found that, while volcanic activity at the bottom of the ocean floor does indeed release CO2, the main carbon input from depth to the atmosphere occurs in continental rift systems.
“Rift systems develop by tectonic stretching of the continental crust, which may lead to break-up of entire plates,” explained lead author Sascha Brune, a researcher at GFZ, according to Phys.org. “The East African Rift with a total length of 6,000 km is the largest in the world, but it appears small in comparison to the rift systems which were formed 130 million years ago when the supercontinent Pangea broke apart, comprising a network with a total length of more than 40,000 km.”
The team made this discovery by using plate tectonic models of the past 200 million years to reconstruct how the global rift network evolved over time. This allowed them to prove the existence of two major periods of enhanced rifting that occurred between 130 and 50 million years ago.
Then, researchers used numerical carbon cycle models to simulate the effect of increased CO2 degassing from the rifts. This revealed that both rifting periods correlate with higher CO2 concentrations in the atmosphere at that time. That finding not only helps scientists better understand the today’s climate shifts, but it also sheds light on the natural carbon shifts that occur throughout the world.
“The global CO2 degassing rates at rift systems, however, are just a fraction of the anthropogenic carbon release today,” added Brune, in a statement. “Yet, they represent a missing key component of the deep carbon cycle that controls long-term climate change over millions of years.”