The breakup of the South Atlantic region, which led to the separation of the African and South American continents, is a well-known global phenomenon. In fact, the famous continental drift theory put forth by the German climatologist, Alfred Wegener, is based on the South Atlantic breakup. According to this theory, the continental plate floats on the oceanic crust and, powered by the Earth's rotation and tidal energy, drifts relative to it. However, the driving forces behind these continental plate movements have not been fully ascertained and continue to be a topic of debate.
Specifically, none of the multiple hypotheses put forth can reasonably account for the formation of numerous linear ridges with continental fragments floating in the Atlantic Ocean. Moreover, these hypotheses do not explain why the opening of the Atlantic Ocean is wider in the south than in the middle.
Now, in a new study, researchers from China seem to have finally solved the conundrum. The team comprising Dr. Liang Guanghe from Chinese Academy of Sciences and Prof. Yang Weiran from China University of Geosciences have proposed a new dynamic model that suggests that while thermal energy can cause the continental plates to drift, the main driving force is supplied by a gravitational slip of the continental crust and hot mantle upwelling. One can picture this better by imagining a slab of butter floating a hot pan, which can move in any direction by itself. This paper was made available online on 07 January, 2022 and was published in Volume 29 Issue 1 of the journal Earth Science Frontiers in January 2022.
How did the duo accomplish this feat? To start with, they studied two deep seismic reflection survey profiles across the Atlantic Ocean, and calculated the magnitude of crustal gravitational slip shear force in the African continent along Moho (the boundary layer between the earth's crust and mantle), in two passive continental margin basins.
This led to two important findings: the continental drift relies on its own gravity to drift via constant rising of the mantle, suggesting that the gravitational slip force is the main driver, and the slip only occurs on the Moho surface due to the greater thickness of the continental crust as compared to that of the oceanic crust, causing the drift to produce an even greater gravity slip.
Based on these findings, the duo established their model of continental drift, according to which the driving force on both sides of the Atlantic Ocean is a self-driving continental crustal movement under gravity.
"The resultant mantle upwelling leads to an inclined Moho surface, on which the continental plate begins to slide, owing to its own weight," explains Dr. Liang Guanghe. "This continuous movement of continental plates causes further mantle upwelling and steepening of the Moho slope, eventually resulting in the drifting of the continental plate above the oceanic plate."
Using this model, the team reconstructed the history of the South Atlantic breakup process. They found that the driving force behind the African plate movement along the Moho is greater in the South than the middle South Atlantic region, causing the southern part of the African region to drift at a much greater speed. This explained the wider opening of the southern part of the Atlantic Ocean.
Furthermore, the model also explained why there are smaller continental fragments scattered in the Atlantic Ocean. In fact, the linear ridges in the Atlantic Ocean are simply the initial continental blocks which stretched out and broke into smaller fragments.
Additionally, the model can also answer questions such as why India is drifting northward, and how the islands of New Zealand, Iceland, and Japan formed.
What are the implications of these findings? Dr. Liang Guanghe says, "While Wegener was right about continental drift, he was wrong about the driving force. The new explanation offered by our model will vastly change the way people understand the movement of plates on earth."
That, indeed, deserves to be called "groundbreaking."
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Reference
DOI: https://doi.org/10.13745/j.esf.sf.2021.12.27-en
Authors: Liang Guanghe1,2,3, Yang Weiran4
Affiliations
1Key Laboratory of Mineral Resources Research, Institute of Geology and Physics, Chinese Academy of Sciences, Beijing, China
2Innovation Academy of Earth Sciences, CAS, Beijing, China
3University of Chinese Academy of Sciences, Beijing, China
4School of Earth Sciences, China University of Geosciences, Wuhan, China
About Earth Science Frontiers
Earth Science Frontiers is a bimonthly peer reviewed scholarly journal co-sponsored by the China University of Geosciences (Beijing) and Peking University. It was first published in 1994, and academician Wang Chengshan is the current Editor-in-Chief. Each issue of the journal is centered on a specific geoscience topic and managed by experts in that field as Guest Editors. Each issue also contains a number of articles on self-select subjects. Articles published on Earth Science Frontiers cover all disciplines of earth sciences with emphasis on frontier and innovative basic research. At the same time, the journal also publishes research findings that may be considered contentious. Over the years, Earth Science Frontiers has won several publisher awards, including "The Internationally Most Influential Journal in Chinese Language" and "The Top 100 Outstanding Chinese Scholarly Journals." In 2019, Earth Science Frontiers was selected among top-tier journals to join a national action plan for achieving excellence in science and technology research publishing in China.
Website: http://www.earthsciencefrontiers.net.cn
About Dr. Liang Guanghe
Dr. Liang Guanghe is a well-known geophysicist with a PhD in Geophysics from the University of Petroleum in China. He is currently affiliated with the Institute of Geology and Geophysics at the Chinese Academy of Sciences (CAS). His interests involve structural, field and exploration geology, mineralogy, geological processes, tectonics, sedimentology, and geography. He has traveled across the world to conduct research on geological phenomena and minerals. He has 33 publications with over 300 citations to his credit.
