Revealed- How world's biggest volcanoes are formed

A new study has solved the 168-year-old mystery of how the worlds biggest and most active volcanoes formed in Hawaii.

The findings led the Australian National University (ANU) by found that the volcanoes were formed along twin tracks due to a shift in the Pacific plates direction three million years ago.

The Pacific Plate is a tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate on the Earth.

The scientists had known of the existence of the twin volcanic tracks since 1849, but the cause of them had remained a mystery until now, said lead researcher Tim Jones from Australian National University (ANU).

Jones, a PhD student from the ANU Research School of Earth Sciences (RSES) said, "The discovery helps to better reconstruct Earths history and understand part of the world that has captivated peoples imagination."

The analysis we did on past Pacific plate motions is the first to reveal that there was a substantial change in motion 3 million years ago.

Jones said, "It helps to explain the origin of Hawaii, Earths biggest volcanic hot-spot and one of the most popular tourist destinations in the world."

Twin volcanic tracks exist in other parts of the Pacific, including Samoa, and the new study published in the journal Nature found that these also emerged three million years ago.

Jones said this kind of volcanic activity was surprising because it occurred away from tectonic plate boundaries, where most volcanoes are found.

He said, "Heat from the Earths core causes hot columns of rock, called mantle plumes, to rise under tectonic plates and produce volcanic activity on the surface."

Jones said,"Mantle plumes have played a role in mass extinctions, the creation of diamonds and the breaking up of continents."

The twin volcanic tracks emerged because the mantle plume was out of alignment with the direction of the plate motion, said co-researcher Rhodri Davies from RSES.

Davies said,"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."

"Plate shifts have been occurring constantly, but irregularly, throughout Earths history. Looking further back in time we find that double tracks are not unique to young Hawaiian volcanism - indeed, they coincide with other past changes in plate motion," said Davies.

Hawaii sits at the south-eastern limit of a chain of volcanoes and submerged sea-mounts which get progressively older towards the north west.