Tectonic swerve responsible for creation of Hawaiian islands


A change in direction of the Pacific Plate 3 million years ago created the conditions for turbulent volcanic eruptions, writes Andrew Masterson.


Pu‘u ‘O‘o, a volcanic cone on Kilauea, Hawaii.
G. E. Ulrich

Hawaii was born in fire and eruption and today boasts the biggest and most active volcanoes in the world – a fact that has long puzzled geologists.

The islands – which together comprise 20 extinct or active volcanoes – are situated well away from tectonic plate boundaries, the moving stress zones that typically produce volcanism.

Now, however, questions surrounding the mysteries of Hawaii’s origin have been answered, thanks to research led by Tim Jones from Australian National University.

The research, published in Nature, found that the volcanoes were catalysed three million years ago by a sudden change of direction by the Pacific Plate, the 103-million-square-kilometre tectonic plate that has Baja California at one end, New Zealand at the other – and Hawaii pretty much in the middle.

As early as 1849, geologists – notably American explorer James Dwight Dana – suggested that Hawaii arose because the earth beneath the seabed was moving in two directions.

In 1963, Canadian geophysicist J. Tuzo Wilson developed the theory by posting the existence of a “hot spot” – a section of the mantle through which a thermal plume rises, melting the rock above. Magma from beneath the mantle rises up, and forms a volcano. Gradually, each new volcano moves away from the hotspot, which then repeats the process.

Indeed, the volcanoes and submerged mountains that extend northwest from Hawaii grow progressively more ancient the further away they are from the islands.

Using complex computer modeling, Jones and colleague Rhodri Davies have effectively confirmed Dana’s and Wilson’s insights.

“The analysis we did on past Pacific Plate motions is the first to reveal that there was a substantial change in motion three million years ago,” says Jones.

“It helps to explain the origin of Hawaii, Earth’s biggest volcanic hotspot.”

Once the critical section of the Pacific Plate had shifted course, its movement was at odds with the force of the thermal plume, thus creating the conditions for turbulent eruptions.

The change of direction that caused the volcanic birth of the islands is not unique. Jones said something similar happened to bring Samoa into existence, at roughly the same time.

Three million years might seem like a very long period, but in geologic terms it is nothing special. At some point in the future, the researchers predict, the misalignment of plate and plume may well fix itself.

“Our hypothesis predicts that the plate and the plume will realign again at some stage in the future, and the two tracks will merge to form a single track once again,” says Davies.

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Andrew Masterson is an author and journalist based in Melbourne, Australia.
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