An international team of scientists from the University of Southampton and the University of Potsdam has provided a fresh look at a long-standing geological puzzle – the presence of continental rock fragments in remote ocean volcanoes.
Their findings were published in the journal Nature Geoscience. The new explanation is based on the idea of a gradual sloughing off of the lower layers of the continents. According to the study, as continental plates move away from each other, the hot upper mantle impacts their bases, initiating so-called “mantle waves.”
“These slow-rolling instabilities at depths of 150-200 km have the potential to rip apart pieces of continental crust and transport them thousands of kilometers,” explains lead author Thomas Gernon of the study.
He notes that unusual “contamination” in certain areas of the oceanic mantle has puzzled geologists for decades, and that existing theories such as subduction or mantle plumes do not offer a comprehensive explanation for the observed chemical anomalies. Co-author of the study, Sascha Bruhn, emphasized that the mantle continued to be affected by the breakup of the continents long after they actually broke apart.
“This system continued to transport enriched material even after the formation of the new ocean basin,” he added.
A chain of underwater volcanoes in the Indian Ocean, formed after the breakup of the supercontinent Gondwana, provides further evidence to support this theory. The absence of signs of mantle plumes and the characteristic decrease in volcanic activity in this area are completely consistent with the proposed model. Scientists say the detected mantle waves could be key to understanding other geological phenomena, from diamond-bearing magma eruptions to the formation of the planet's largest topographic features.
