Researchers Solve Ancient Volcanic Mystery
Study Pinpoints Source of 120M-Year-Old Super-Eruption, Explains Submerged Pacific Seafloor
UMD researcher Val Finlayson (left) and study collaborator Paulo Galvan recovering rock samples from a dredge while at sea in the Pacific Ocean.
Photo by Val Finlayson
Geologists led by the University of Maryland and the University of Hawaii have connected the dots between one of the largest volcanic eruptions in Earth’s history and its source deep beneath the Pacific Ocean following years of uncertainty among scientists.
In a paper published Wednesday 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, an assistant research scientist in UMD’s Department of Geology. “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.”
Scientists had long wondered whether the southern Pacific Ocean’s Louisville hot spot—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 hot spot track was subducted, or pushed, under tectonic plates in the Pacific region,” Finlayson said. “We had to sample deeply submerged volcanoes from a different long-lived hot spot track to find evidence from tens of millions of years ago that suggested our models for the Pacific plate needed revision.”
In addition to researchers from the UMD and the University of Hawaii, co-authors include researchers from Oregon State University, University of South Carolina, University of California Santa Barbara and Brown University.
Co-lead scientists Jasper Konter and Matt Jackson look for a suitable sampling site using data of seamount collected with the research ship's sonar system.
Finlayson and her team 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 the volcano’s “footprints.” Volcanic tracks are formed by successive eruptions as the Earth’s crust (composed of tectonic plates) moves over deeper hot spots over millions of years.
“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.”
Finlayson’s team plans to apply its improved models to better understand other ancient volcanic features scattered across the ocean floor and above its surface. Not only could this work further understanding of the literal foundations of many Pacific island nations that sit atop volcanic platforms and underwater volcano chains, she believes that her team’s discovery will aid scientists studying volcanism and geological evolution around the world.
“We’ve solved one mystery, but there are countless more waiting to be unraveled,” Finlayson said. “Everything new we learn about the Earth’s tumultuous past helps us better understand the dynamic planet we live on today.”
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