The Earth’s mantle was divided into two regions: the African region and the Pacific region when the supercontinent Pangaea broke apart.
The mantle of the Earth is separated by the Pacific Ring of Fire, an ancient structure reflecting the formation and destruction of the supercontinent Pangaea. One side contains the majority of the land on Earth. Named the African region, this area extends from the eastern coastal regions of Asia and Australia to Europe, Africa, and the Atlantic along the western coast of North America. The remaining area is the Pacific region, which includes the ocean of the same name. Below the African region, the mantle contains many elements and their isotopes with a much greater diversity than the Pacific region, according to Live Science.
Earth was once covered by a single supercontinent: Pangaea. (Image: How Stuff Works).
This reflects the last two supercontinent cycles over the past billion years, according to co-author Luc Doucet, a geoscience and planetary researcher at Curtin University in Australia. During that time, two supercontinents existed, the first being Rodinia (which formed around 1.2 billion years ago and broke apart 750 million years ago), and Pangaea (which formed around 335 million years ago and broke apart 200 million years ago). “What we observe today is essentially what happens during the transition from Rodinia to Pangaea and then the breakup of Pangaea,” Doucet stated.
These supercontinents merged in the African region. As the ocean closed between them, the oceanic crust slid beneath the continental crust in a process known as subduction, sometimes dragging continental rocks down with it. This activity brought elements and isotopes from the continental crust down into the mantle beneath the developing supercontinent, Doucet explained. This geological conveyor belt continued in slightly different forms even after the supercontinent was formed. The oceanic crust at the edge of Rodinia and later Pangaea sank beneath the continental crust, eroding parts of the continental rock. This process created a funnel effect.
Even after Pangaea broke apart, signs of its existence remained in both shallow and deep mantle, according to research published in the journal Nature Geoscience. Doucet and Zheng-Xiang Li, an emeritus professor at Curtin University, focused on the magma of the shallow mantle in their new study. They examined 3,983 samples from mid-ocean ridges, where tectonic plates are moving apart and magma from the shallow mantle rises, solidifying into volcanic rock or basalt.
The research team then used machine learning to compare the elemental and isotopic compositions of basalt samples from around the world and from the same period. Similar to magma from the deep mantle, they found that the shallow mantle is divided into the African and Pacific regions. These findings reveal more about the processes that bind the mantle to the Earth’s surface.
