When it comes to carbon emissions in our atmosphere, a major producer was at work long before humans began spewing greenhouse gases from factories and vehicles: Earth itself.
Continental rifting – the process in which continents break apart from one another – releases massive amounts of carbon dioxide into the air.
A team of scientists from Potsdam’s GFZ German Research Centre for Geosciences recently turned their focus on rifting, to discover whether the shifting of the Earth’s tectonic plates has more or less of an effect on atmospheric carbon than underwater volcanic activity.
More than 99 percent of the carbon on Earth is captured deep underground. Volcanic activity can allow some of this carbon to escape in gas form and enter the atmosphere.
However, the team led by Dr. Sascha Brune found that continental rifting releases much more carbon dioxide from under the Earth’s surface.
“Rift systems develop by tectonic stretching of the continental crust, which may lead to break-up of entire plates,” Brune said. “The East African Rift with a total length of [more than 3,720 miles] 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 [24,800 miles].”
Using scientific models, the team worked backwards to see where and how active rift systems may have been during the past 200 million years of Earth’s history. They found that 50 million and 130 million years ago, rift systems may have been much larger and more active than at other points in geological history.
When they compared their findings against models showing the makeup of the Earth’s atmosphere during those periods, they found spikes in atmospheric carbon.
Human activity releases more carbon dioxide than continental rifting does, Brune noted.
“The global [carbon dioxide] degassing rates at rift systems, however, are just a fraction of the anthropogenic carbon release today,” he said. “Yet, they represent a missing key component of the deep carbon cycle that controls long-term climate change over millions of years.”
Continental rifting is the process by which a continent is stretched and pulled apart, leading to the formation of a new ocean basin. It occurs when the Earth’s tectonic plates move away from each other, causing the lithosphere, which is the rigid outer layer of the Earth, to crack and separate.
This process is typically associated with a significant amount of seismic activity and volcanic activity, as magma rises from the mantle and fills the gaps created by the separating plates.
Over time, the continued movement and separation of the plates can lead to the formation of a rift valley, a long, narrow depression in the Earth’s surface that can be hundreds or thousands of kilometers long. As the plates continue to move apart, the rift valley can widen and deepen, and eventually become a new ocean basin.
Continental rifting is an important geological process that helps shape the Earth’s surface and can have significant impacts on the environment, including the formation of new ecosystems and the potential for natural resources such as minerals and oil.
A rift system is a network of interconnected faults and rift zones that are associated with continental rifting. It can be composed of several rift segments that are aligned along a common axis and are separated by areas of relative stability or weakness in the Earth’s crust.
Rift systems are characterized by active geologic processes, including seismic activity, volcanic activity, and the uplift and subsidence of the Earth’s surface. As the continental plates move apart, the tensional stresses that result can cause the crust to stretch and thin, leading to the formation of faults and rift valleys.
One of the most famous rift systems in the world is the East African Rift System, which stretches for over 3,000 km through East Africa and is associated with the formation of several lakes, including Lake Victoria and Lake Tanganyika. The Rio Grande Rift is another example of a rift system, located in the southwestern United States and stretching from Colorado to Mexico.
Rift systems are important features in the study of plate tectonics and the evolution of the Earth’s crust. They provide insights into the processes that shape the Earth’s surface and can have significant impacts on the environment and human societies.
The study has been published in the journal Nature Geoscience.
By Kyla Cathey, Earth.com staff writer
Image credit: Dr. Sascha Brune, NASA WorldWind