A new study reveals that Earth’s mantle is divided by the Pacific Ring of Fire, a geological scar reflecting the formation and breakup of the supercontinent Pangaea.
One of Earth’s regions, known as the African domain, encompasses most of the planet’s landmass. It extends from the east coasts of Asia and Australia, across Europe, Africa, and the Atlantic, to the west coast of North America. In contrast, the Pacific domain primarily covers the Pacific Ocean. According to new research, the mantle beneath the African domain contains a greater diversity of elements and isotopes compared to the Pacific domain.
This distribution reflects the last two supercontinent cycles over the past billion years, explained Luc Doucet, a senior research fellow in Earth and planetary sciences at Curtin University, in an interview with Live Science. During this period, two supercontinents emerged: Rodinia, which formed approximately 1.2 billion years ago and broke apart about 750 million years ago, and Pangaea, which formed around 335 million years ago and began breaking up 200 million years ago.
“What we observe today is essentially the result of transitions from Rodinia to Pangaea, followed by the breakup of Pangaea,” Doucet noted.
Both supercontinents formed over what is now the African domain. As oceans closed between landmasses, the oceanic crust was forced beneath the continents in a process called subduction, occasionally dragging pieces of continental rock into the mantle. This mechanism transported elements and isotopes from the continental crust into the mantle beneath the emerging supercontinent, Doucet explained.
Once the supercontinents were assembled, the process shifted slightly: oceanic crust on the edges of Rodinia and later Pangaea continued to subduct beneath the continents. This subduction eroded portions of the continental rock, creating a funnel effect as tectonic plates collided and ground together.
“You concentrate everything below the supercontinent,” he said.
According to the study, even after the breakup of Pangaea, its geochemical signatures remained in both the deep and shallow mantle. The findings were published in the journal Nature Geoscience.
Building on their 2020 research on magma from the deep mantle, Luc Doucet and Zheng-Xiang Li, a professor emeritus at Curtin University, shifted their focus to shallow mantle magma in this new study. They analysed the chemistry of 3,983 samples collected from mid-ocean ridges, where tectonic plates are spreading apart and magma from the shallow mantle rises and solidifies into volcanic rock, such as basalt.
These findings provide new insights into the link between Earth’s mantle and its surface, Doucet explained. While the exact reasons for supercontinent breakup remain unclear, it is believed to involve the rise of hot mantle material from deep regions called large low-shear velocity provinces (LLSVPs), or mantle “blobs.” Two such blobs exist: one beneath the Pacific domain and the other beneath the African domain, the Live Science reported.
“The composition of mantle domains reflects not only surface processes but also activity deep within Earth,” Doucet noted. Understanding these dynamics can help geoscientists identify regions where valuable mantle materials, like rare earth elements critical for modern technology, might be concentrated. Additionally, plate tectonics play a key role in cycling essential elements for life, such as carbon and zinc, from Earth’s interior to its surface, highlighting the importance of an active planet in fostering and sustaining life.
“Earth is the only known planet with plate tectonics,” Doucet said, “and we want to understand how this system works and why it is so unique.”
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