Earth scientists from the University of Hawaiʻi at Mānoa, University of Maryland and others finally connected the dots between one of the largest volcanic eruptions in Earth's history and its source deep beneath the Pacific Ocean.
In a paper published April 30 in the journal Nature , the team revealed that the same underwater hotspot created both a chain of underwater volcanoes in the southern Pacific region and the massive Ontong-Java Plateau, the largest volcanic platform on Earth.
"Up until now, we've had this extremely disconnected picture of the Pacific and its volcanoes," said the study's corresponding author Val Finlayson, who was a graduate student in the Department of Earth Sciences at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST) when this study began. "But for the first time, we're able to make a clear connection between the younger southern and older western Pacific volcanic systems. It's a discovery that gives us a more complete history of how the Pacific Ocean basin has evolved over millions of years to become what it is today."
For years, scientists wondered whether the southern Pacific Ocean's Louisville hotspot—an area where hot and chemically distinct material from deep inside the Earth rises to the surface to create volcanoes—formed both the underwater mountain chain bearing its name and the 120-million-year-old Ontong-Java Plateau, a submerged seafloor platform located what is now north of the Solomon Islands. Previous theories and models on how the Pacific seafloor moved attempted to explain the connection between the two major geological features but failed to provide a definitive answer.
"Much of the physical evidence for a connection between Louisville and Ontong-Java has disappeared because part of the Louisville hotspot track was subducted, or pushed, under tectonic plates in the Pacific region," said Finlayson, who is now an assistant research scientist in the University of Maryland's Department of Geology. "We had to sample deeply submerged volcanoes from a different long-lived hotspot track to find evidence from tens of millions of years ago that suggested our models for the Pacific plate needed revision."
Finlayson and co-authors from UH Mānoa, Oregon State University, University of South Carolina, University of California Santa Barbara and Brown University, made their first breakthrough when they discovered a series of underwater mountains near Samoa that were much older than expected for volcanoes in the area.
By analyzing the age and chemical makeup of ancient rock samples taken from the area, the researchers concluded that these mountains were part of a much older segment of the Louisville volcanic track, which Finlayson compared to a volcano's "footprints." As the Earth's crust (tectonic plates) moves over hotspots, they form these volcanic tracks.
"We can track these 'footprints' across time and space," Finlayson explained. "The footprints get progressively older as you move away from an active hot spot, similar to how your own footprints will fade away in the sand as you walk. But you can still tell that these prints belong to the same source. Thanks to this new evidence, we were able to revise current models of Pacific plate motion and gain a better understanding of how the seafloor has moved over millions of years."
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