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CORVALLIS, Ore. – A new study using argon dating techniques has confirmed that the “hotspot” forming the Hawaiian islands drifted rapidly off course between 60 million and 48 million years ago before stabilizing, while other hotspot chains show more subdued movements.

The new study, published this week in the journal Nature Communications, outlines how an international science team traced the formation of the Rurutu volcanic chain in the western Pacific Ocean to a long-lived, but newly identified mantle plume forming a “hotspot.” The team went back in time along this new hotspot utilizing the same dating techniques used to analyze the Hawaiian and Louisville chains in the Pacific Ocean.

Their study confirms just how unique the Hawaiian island chain is. Unlike the Rurutu and Louisville chains, which have moved in concert with the movement of tectonic plates, the hotspot that formed Hawaii “drifted” surprisingly fast off course beginning millions of years ago and in a direction away from the movement of the subducting plate.

“The new dating of the three Pacific hotspots provides striking evidence that the Hawaiian island chain is significantly different than its cousins,” said lead author Kevin Konrad, an Oregon State University faculty research assistant who conducted much of the research as a doctoral student at OSU.

“Beginning some 60 million years ago, the Hawaiian hotspot moved southward and at a relatively quick pace, while Rurutu and Louisville remained fairly constant. No one is sure just why it happened, but the movement ended about 48 million years ago, and all three hotspots have been stable since.”

A hotspot is a location on the Earth’s lithosphere where streams of hot mantle material originating from the deepest portions of the lower mantle comes to the surface, where it is cooled and creates land masses in the form of volcanic islands. When the lithosphere moves under tectonic forces across the Earth’s surface it leads to the formation of volcanic island chains above and under water.

Konrad said there are two primary hypotheses why the Hawaiian hotspot drifted, though neither has been proven. Some scientists believe that the lower mantle in the region became deformed during subduction, and that the subducting plate rolled backwards, pushing into the base of the mantle where the Hawaiian plume originates.

Other researchers say the Hawaiian plume was “captured” by the Kula Ridge, an extinct mid-ocean spreading center where the Pacific tectonic plate was fabricated.

“Numerical models have shown that plume conduits can be pulled toward regions of mantle upwelling, such as spreading centers,” Konrad said. “Therefore the southward drift of the Hawaiian plume some 60 million years ago may represent the plume moving away from this ancient spreading center and back toward a more lateral position some 20 million years later.”

The research was supported by the National Science Foundation. Other researchers on the study include Anthony Koppers, Oregon State University; Bernhard Steinberger, GFZ German Research Center for Geosciences and the University of Oslo; Valerie Finlayson and Jasper Konter, University of Hawai-Manoa; and Matthew Jackson, University of California, Santa Barbara.

Konrad and Koppers are with OSU’s College of Earth, Ocean, and Atmospheric Sciences.