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Ocean's journey towards the centre of the earth

11 March 2009

A Monash geoscientist and a team of international researchers have discovered evidence of links between New Caledonia and New Zealand, areas of the South Pacific thought to be geographically isolated.

Using computer modelling Wouter Schellart and the team reconstructed a prehistoric cataclysm that took place when a tectonic plate between Australia and New Zealand sank 1100 kilometres into the earth's interior and at the same time formed a long chain of volcanic islands at the surface.

Mr Schellart conducted the research in collaboration with Brian Kennett from ANU (Canberra) and Wim Spakman and Maisha Amaru from Utrecht University in the Netherlands.

"Until now many geologists have only looked at New Caledonia and New Zealand separately and didn't see a connection," Mr Schellart said.

"In our new reconstruction we saw a large number of similarities between New Caledonia and northern New Zealand in terms of geology, structure, volcanism and timing of geological events.

"We then searched deep within the earth for proof of a connection and found the evidence 1100 kilometres below the Tasman Sea in the form of a subducted tectonic plate."

Mr Schellart said the new discovery diffused debate about whether the continents and micro-continents in the Southwest Pacific had been completely separated since 100 million years ago.

"We are now able to say a tectonic plate about 70 km thick, some 2500 km long and 700 km wide was subducted into the earth's interior, providing a geographical connection between New Caledonia and New Zealand between 50 and 20 million years ago by a long chain of volcanic islands," Mr Schellart said.

"This discovery could be important for the migration of certain plant and animal species at that time."