Australasian Science: Australia's authority on science since 1938

Geologists Find a Piece of Australia under Vanuatu

A fragment of Australia found beneath Vanuatu may cause a rethink about how continents are built.

Geologists have thought that the volcanic Vanuatu islands, about 2200 km east of Townsville, were isolated from continental influences, but now research by James Cook University scientists suggests that Vanuatu’s “geological basement” contains ancient material from northern Australia.

The team discovered that volcanic rocks from Vanuatu contained tiny crystals of zircon that were carried up in magma. Radiometric dating estimated that the crystals were up to three billion years old.

Dr Carl Spandler said the zircon crystals “shouldn’t be there,” and its presence has major implications for how scientists understand how continents are made. “The range of ages of the zircon crystals from Vanuatu closely matches the age of rocks that make up northern Australia,” he said. “There is nothing else like it in the south-west Pacific.”

The fragment of Australian crust now under Vanuatu could have separated from the mainland prior to the Cenozoic Era around 100 million years ago.

“Just because island chains or landmasses may be far removed from each other today doesn’t mean that they always were,” Spandler said. “This calls for a rethink of how we calculate the rates and processes of generating new crust on Earth.”