For decades, geologists have been puzzled by a major enigma at the bottom of the Pacific Ocean: where did the lava come from that formed the Ontong Java Plateau—the largest volcanic structure ever discovered on Earth? Now, a recent study has finally uncovered the answer.
A team of scientists from the University of Maryland and the University of Hawai‘i has successfully linked two massive geological features that previously seemed unrelated: the vast Ontong Java Plateau and an underwater volcanic chain known as the Louisville Ridge.
Their study, published in the journal Nature on April 30, 2025, offers new insights into the volcanic history and tectonic plate movements of the Pacific.
A Trail-less Mystery
Located north of the Solomon Islands, the Ontong Java Plateau formed around 120 million years ago and is larger in area than the state of Alaska.
Despite its massive size, its existence is puzzling because it lacks the typical “volcanic trail” found at hotspots—regions where hot magma from the Earth’s interior rises to form a chain of volcanoes as tectonic plates move above it.
Such trails are clearly visible in hotspot chains like the Hawai‘i-Emperor Seamounts or the Louisville Ridge. But in the case of Ontong Java? Nothing.
This absence of a trail has long baffled scientists. How could such a massive structure have formed without leaving the usual track of migrating volcanic activity?
Some theories suggested that the hotspot responsible may have drifted far from its original location. However, paleogeographic data indicates that the heat source beneath the Louisville Ridge has remained relatively stable for tens of millions of years.
Ancient Footprints on the Ocean
Instead of searching directly along the Louisville Ridge—parts of which have already been subducted beneath the Earth's crust due to tectonic movement—the research team, led by Val Finlayson, took a different approach.
They investigated seamounts near Samoa and the Rurutu–Arago region, areas known to have volcanic histories stretching back more than 100 million years.
Near Wake Island, the team discovered deep-sea volcanic rocks with chemical compositions similar to those produced by the Rurutu–Arago hotspot. This provided a key clue: these ancient features may actually be part of a "footprint" left behind by ancient magma flows.
These geological patterns enabled researchers to trace the historical movement of tectonic plates. “The footprints get progressively older as you move away from an active hotspot, similar to how your own footprints fade in the sand as you walk—but you can still tell they came from the same source,” explained Val Finlayson, a marine geologist from the University of Maryland and lead author of the study.
Re-Mapping the Movement of the Pacific Plate
By combining rock age data and unique chemical markers from various hotspots, the team was able to reconstruct the movement of the Pacific Plate between 80 and 100 million years ago.
The results revealed that it wasn't the hotspots that had shifted dramatically over time, but rather the tectonic plate itself that rotated and moved significantly—carrying structures like the Ontong Java Plateau to their current positions.
This discovery directly links the volcanic chain of the Louisville Ridge to the formation of the Ontong Java Plateau. In other words, both features originated from the same magma source but were carried to vastly different locations by the movement of tectonic plates.
Wider Implications
This discovery is not merely about connecting two volcanic features. Many island nations in the Pacific—such as Tuvalu, the Cook Islands, and the Marshall Islands—are built upon ancient volcanic foundations formed by the activity of these hotspots.
By gaining a deeper understanding of how these regions were formed, scientists can more accurately assess geological risks, such as potential volcanic eruptions or future earthquakes.
Furthermore, the study highlights that not all hotspots behave the same way. For instance, between 60 and 50 million years ago, the Hawaiian hotspot appeared to move more independently compared to the Louisville and Rurutu–Arago hotspots.
This distinction is crucial for differentiating between plate movements and shifts originating within Earth’s magma system itself.
Many Mysteries Remain
Although this research has solved a major geological puzzle, scientists acknowledge that many more mysteries still lie hidden beneath the ocean floor. With advancements in seafloor mapping technology, isotope analysis, and increasingly sophisticated plate motion models, researchers hope to uncover more of Earth’s long-buried stories.
