Unlocking Macquarie Island’s geological secrets

A team of ARC-supported researchers embarked on a landmark voyage to shed new light on Macquarie Island’s underlying structure and geological evolution, and also to help with the monitoring of future earthquakes and tsunamis that could affect Australia and New Zealand.

The voyage had a two-fold purpose: to deploy 29 seismometers around the island and produce the first high resolution maps of the seafloor surrounding the island.

Macquarie Island is a UNESCO World Heritage Site and is the only island in the world composed entirely of oceanic crust and rocks from the mantle. The island is a part of the 40,000km-long Ring of Fire – responsible for 90% of the world’s earthquakes – and is the boundary between the Australian and Pacific tectonic plates.

As part of a 2020 ARC Discovery Project, Professor Hrvoje Tkalčić and Dr Caroline Eakin led a team of Australian National University scientists to investigate the region’s crustal and mantle structure as well as its seismicity by deploying seismometers around the island.

Professor Tkalčić said the seismometers would be recovered in late 2021, returning critical data. In the meantime, five seismometers are being deployed on Macquarie Island as part of the project, supported by Geoscience Australia, the Australian Antarctic Division and Tasmania Parks and Wildlife Service, and assisted by their personnel.

‘Our research aims to image Earth structure by using state-of-the-art seismological techniques together with a carefully designed configuration of ocean bottom seismometers pointing towards the Earth’s centre like a giant antenna; and also to shed more light about the physics of the world’s largest underwater earthquakes that are not associated with active subduction.’

At the same time, scientists from the University of Tasmania led by Professor Mike Coffin conducted research to produce the first high-resolution maps of the seafloor surrounding Macquarie Island.

‘The creation of seafloor maps that identify faults, fracture zones, and seafloor spreading centres will give us new insights into the structure, behaviour, and history of this important plate boundary, which presents significant tsunami hazards for both sides of the Tasman Sea,’ Professor Coffin says.

	Macquarie island sits on the highly active tectonic plate boundary between the Australian and pacific plates and generates some of the largest intra-oceanic earthquakes away from subduction zones.