A team of geologists led by the University of Maryland and the University of Hawaiʻi finally connected one of the largest volcanic eruptions in Earth’s history with its source deep beneath the Pacific Ocean.
The Ontong-Java Plateau is a massive, submerged seafloor platform located in the southwestern Pacific Ocean. Several kilometers thick lava flows cover an area roughly the size of Alaska. The erupted volume is several times larger than the famous Deccan Traps in India. The plateau was formed during the Cretaceous, around 116 and 90 million years ago, by one of the largest volcanic eruptions in Earth’s history, but the exact site and source of the volcanism eluded scientists.
For years, they wondered whether the 70-million-year-old Louisville hotspot—an area in the southern Pacific Ocean where hot and chemically distinct material from deep inside Earth rises to the surface to create volcanoes—formed both the underwater mountain chain bearing its name and the Ontong-Java Plateau.
Attempts to link the two major geological features failed to provide a definitive answer because scientists were searching at the wrong spot, as a new study suggests.
“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,” explains study first author Val Finlayson, an assistant research geochemist in University of Maryland’s Department of Geology.
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, they were able to reconstruct how the Pacific plate moved. The results show that the between 80 and 100 million years ago the Pacific plate rotated slightly.
“We can track these ‘footprints’ across time and space. The footprints get progressively older as you move away from an active hotspot, 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 explains.
With the new directions, the team was able to finally link the Ontong-Java Plateau to the Louisville hotspot despite the missing 20 million years. The hotspot was active for much longer than the available rock ages suggest.
“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,” as the researchers explain the missing evidence.
Finlayson’s team now plans to apply their improved models to better understand other ancient volcanic features scattered across the ocean floor and above its surface.
“We’ve solved one mystery, but there are countless more waiting to be unraveled. This finding offers us a more accurate history of the Pacific and its volcanic activity and helps us understand more about the dynamics and style of volcanism that occurs there,” Finlayson said. “Everything new we learn about the Earth’s tumultuous past helps us better understand the dynamic planet we live on today,” concludes Finlayson.
The study,”Pacific hotspots reveal a Louisville–Ontong Java Nui tectonic link,” was published in the journal Nature.
Additional material and interviews provided by the University of Maryland.