Scientists probe inner workings of a submarine volcano

5 JULY 2018

Voyage co-leader Cornel de Ronde superimposed on a 3D image of Brothers submarine volcano showing the cone where scientists drilled to explore the internal plumbing of the volcano. Image – Darren D’Cruz, GNS Science

An international team of scientists with several New Zealand participants has returned from a two-month voyage in the Kermadec Arc bristling with new knowledge about the inside workings of submarine volcanoes.

Using the scientific research ship JOIDES Resolution, they drilled a number of boreholes into the heart of the hydrothermally active Brothers submarine volcano. The main aim of the US$15 million expedition was to learn more about how metals are transported within submarine volcanoes and brought to the seafloor where they form metallic deposits.

Not unexpectedly for such an ambitious mission, there were setbacks. At one point they struck rock so hard and hot fluids so acidic that some of their drilling equipment was destroyed. But this was more than offset by the many successes they chalked up.

Brothers submarine volcano is 400km northeast of the Bay of Plenty coast and is about three times the size of White Island with its summit rising to within 1200m of sea level.

It is the most hydrothermally active submarine volcano in the world, and partly because of this it attracts scientists from many countries. It is the first time Brothers has been probed by deep drilling, although it has been investigated a number of times by surface ships and remotely operated vehicles in the past 20 years.

Voyage co-chief scientist, Cornel de Ronde of GNS Science, said the advanced drilling technology and the approached they used to drill the volcano were key factors in the success of the voyage.

“We exceeded our expectations by some considerable margin and we have now compiled the most comprehensive information ever about the inner workings of a submarine arc volcano,” Dr de Ronde said.

“We recovered about twice as much drill core from inside the volcano as the combined efforts of the two previous expeditions that tried to drill through the volcanic rock of submarine hydrothermal systems.”

The 225m of core recovered underwent preliminary analysis on the ship during the voyage and will now be shared among participating countries for more detailed study.

The initial findings from the voyage are preliminary only and it will take extensive onshore analysis and interpretation of all the data to fully realise the knowledge gains from the expedition. This work will take place simultaneously in science institutions around the world, including New Zealand.

Dr de Ronde said all magmas contained small amounts of metals, but the magma and resultant volcanic rock at Brothers was unusually rich in metals such as copper and gold.

The expedition would help to elucidate where these metals come from, how they accumulate, and what pathways they take to reach the seafloor from inside the Earth’s crust.

Voyage co-chief scientist Susan Humphris, of US-based Woods Hole Oceanographic Institution, said the expedition had also helped scientists better understand what regulates the chemical composition of seawater.

“Chemical reactions between rocks and seawater at depth in the volcano change the chemistry of the fluid that is released into the ocean through hydrothermal vents,” said Dr Humphris.

While the ship is docked in Auckland scientists involved with the project are hosting a nine-day field-based introduction to earth science for early career science teachers and senior high school students from New Zealand and overseas. Called ‘The School of Rock’, it includes a rare opportunity to work on the JOIDES Resolution while it is in port.

The initiative is an annual education programme offered by the 23-nation International Ocean Discovery Program (IODP), which operates the JOIDES Resolution. It will include field trips to explore the geological history of the Auckland region, including the islands of the Hauraki Gulf.

Teachers and science communicators are attending from the United States, Australia and New Zealand. Apart from some meals, costs are covered by IODP and the Australian and New Zealand IODP Consortium.

IODP is an international research collaboration that conducts seagoing expeditions to study Earth’s history and dynamics recorded in sediments and rocks beneath the ocean floor.

The expedition to the Kermadec Arc was funded by the consortium of 23 countries that make up IODP, with the single largest contributor being the National Science Foundation in the United States.

New Zealand’s participation in IODP is coordinated by GNS Science in partnership with other Australian and New Zealand research organisations and universities that make up the Australian and New Zealand IODP Consortium (ANZIC).

This consortium is funded by the Australian Government through the Australian Research Council’s LIEF funding scheme and an Australian and New Zealand consortium of universities and government agencies.

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