Two Buried Supercontinents Under Africa and the Pacific Ocean Could Be Much Older Than Previously Assumed

Earth has several layers between the crust and the core. In a recent study, scientists have looked into the consistency of the mantle that lies beneath the surface and is made up of rocks that have a thickened caramel-like consistency. The region stretches for 1,800 miles and is uniformly blended but other portions of the mantle appear like massive lumps, according to CNN Science. The lumps in the mantle were revealed to be two enormous supercontinents buried beneath the crust and fragments of it remain lodged between the tectonic plates.

The supercontinents lie deep under Africa and the Pacific Ocean. Experts from Utrecht University in the Netherlands analyzed the data obtained from modern methods to monitor earthquakes, which helped them to know about the supercontinents that could be way older than what experts initially believed them to be. Nature published the study, detailing how the discovery adds to a long list of evidence that helped to understand more about the formation of our planet. 

"These findings will contribute to a better understanding of mantle convection and plate tectonics, and, therefore, phenomena we experience at the surface like earthquakes and volcanism," Claire Richardson, a doctoral candidate in the School of Earth and Space Exploration at Arizona State University, who was not involved in the new research, said, per the news outlet over an email. "Resolving the physical, thermal, and chemical properties of rocks 1,864 miles below our feet, at extreme temperatures and pressures, is a challenging problem." The researchers used seismic data to spot the anomalies in the mantle about 50 years ago.

The supercontinents are somewhat like buried islands that tower over 600 miles. "However, little was known about what they were made of when they sank and what role they might play in mantle flow, known as convection," Dr. Sujania Talavera-Soza, lead author of the new study and a geosciences and seismology researcher at Utrecht University, said per the news outlet. "Their origin and whether they are long-lived structures. It’s widely debated. Velocity loss in seismic waves suggested that these mantle zones were hotter than the rocks around them." "There was no information about that," study co-author Dr. Arwen Deuss, a professor of structure and composition of Earth’s deep interior at Utrecht University, explained. "We only knew that seismic waves slowed down."

Deuss also revealed how there are other sunken tectonic plates around the supercontinents. "The fact that the LLSVPs show very little damping means that they must consist of much larger grains than their surroundings," Talavera-Soza continued. "Our study points to the LLSVPs being long-lived features, at least half a billion years old, perhaps even older. This implies they act as anchors at the base of the core-mantle boundary and have survived mantle convection, meaning that the mantle is not well-mixed." The recent discoveries could transform the understanding of tectonic plates and how their movement could have shifted these ancient masses deep inside the mantle.

It is believed that further analysis of these supercontinents in the future could reveal if they are the source of geochemical elements as old as Earth itself and are found in certain types of volcanic eruptions. "These LLSVPs have been there for a long time — if they’ve been there for a billion years, they might have also been there for four billion years. They might well be that hidden reservoir where these chemical primordial elements might be located. We can’t prove that now, but geochemists can investigate this," Deuss concluded. "From this study, I think there will be a lot of extra research that might answer a lot of outstanding questions that have been confusing scientists for ages."