Q & A with Professor Neville Exon

Q & A with Professor Neville Exon
Exploring the Earth Under the Sea
28 November 2017

Join Professor Neville Exon for the launch of this book at the Library on Thursday 7 November.

Recently, Professor Exon sat with us to to chat about the book, and shed some light on this important, and fascinating, research program.

Tell us about the book.

Exploring the Earth under the Sea brings to life the world’s largest and longest-lived geological research program, which has been drilling over many decades at many locations deep below the ocean floor, to recover continuous cores of sediment and rock. Study of these materials has helped us understand how the Earth works now, how it has worked in the past, and how it may work in the future. The cores are a wonderful source of information on the dynamic processes that form and reform the Earth, both beneath the ocean and on land. The results have revealed climate and oceanographic change on different time frames, the history of life in the sea and on land including global mass extinctions, the extraordinary story of the great masses of ‘extremophile’ microbes that live beneath the sea bed, the nature of the giant earthquakes and tsunamis generated at the trenches where tectonic plates collide, and the nature of submarine volcanoes and metalliferous deposits.

This book outlines the technology and enduring international partnerships that underlie the scientific ocean drilling accomplished by the first phase of IODP (Integrated Ocean Drilling Program) from 2008 to 2013. IODP currently involves 23 countries and has an annual operational budget of $US180 million. The book highlights the important role of Australian and New Zealand scientists in the program, and the great scientific benefits we have derived from our partnership since joining IODP in 2008. As well as the scientific summaries, there are also personal accounts by shipboard scientists of how they found life at sea on two-month expeditions, working 12-hour shifts on a noisy drill ship.

Photo courtesy of JOIDES Resolution Science Operator, Texas A&M University 

What motivated you to produce the book?

I have worked as a geologist on land and at sea for many years, in and off Australia and around the world. I first got seriously involved in scientific ocean drilling in the 1980s, went on my first expedition, off northwest Australia, in 1988, and led an expedition around and south of Tasmania in 2000. I found the program scientifically fascinating and very rewarding personally and, when Australia was successful in joining IODP in 2008, started as the program co-ordinator for Australia and New Zealand at ANU, only retiring from this position in September this year. That role involved dealing with our international and Australian partner institutions, helping plan or encouraging others to plan drilling proposals for work in our region, many of which led to expeditions, and encouraging scientists of all ages to become directly involved in IODP expeditions or to work on a selection of the 400 km of legacy cores held in repositories around the world.

When the first phase of IODP was completed in 2013, I decided to take the lead in telling the story of what we had accomplished in the six years in which we were members, and had very strong support from our community. Australia and New Zealand can be proud of what we accomplished in that period and we believe that this fascinating story should be more widely known.  

Map, courtesy of Nick Mortimer, GNS Science, Dunedin  

Why is the Integrated Ocean Drilling Program story significant to Australia and New Zealand?

Scientific ocean drilling has built up a coherent story of the history of the oceans over many millions of years, and that story also sheds light on the history of the land. In essence, the nature of the land, including its topography, its rainfall, and its endowment of soils and mineral resources, depends entirely on the plate tectonics that are driven by the convection currents that form the oceans and the land. Our rainfall depends on where we sit in the world’s oceans at present, and also on the mountain building, past and present, that is related to the configuration of the tectonic plates. A large proportion of the rocks on Australia, igneous, volcanic and sedimentary, were laid down in the ocean, and later welded to the land by tectonic forces. Many of our soils are old and spent because of the lack of mountain building for more than 100 million years, during which time the land was slowly eroded and the soils deeply weathered. The best soils are generally in the south and east of Australia (for example in western Victoria) – where there has been outpouring of basalt from innumerable vents over many millions of years, as Australia moved northward some 2000 km from Antarctica and conduits developed between deep magma chambers and the land surface. 

Many of the clues to our land history are found in the ocean in the sediments that have been shed from the land, and similar sediments are not common or poorly preserved on land. They tell us about the conditions on land: was there uplift and rapid erosion in some areas, what is the nature of the clays and dust that came from land, what vegetation was there on land in different areas? These sediments and their contained microfossils also tell us about the changing oceanic conditions that strongly affect rainfall - sea surface temperatures and current circulation. They are providing evidence of the great drying that occurred on much of Australia in the last few million years as it moved northward into the latitudes that support the great deserts of the world. The drying is exacerbated by the cooling of the world as we moved into the ice ages. Rapid past climate changes are well documented in IODP cores, and this information is useful in considering controls on the rapid global warming that we see at present.

Tell us about the sunken continent of Zealandia.

There has been very substantial global media coverage of the story of Zealandia, a sunken continent that is about two-thirds the size of Australia, in relationship to the recent IODP Expedition 369, which was carried out over it by the high-technology drill ship JOIDES Resolution (photo courtesy of JOIDES Resolution Science Operator, Texas A&M University). The continent was continuous with eastern Australia 75 million years ago, but tectonic forces moved it anti-clockwise away to the east and stretched it so that it was thinned and sank beneath the waves. However, a change in global plate tectonic configuration about 53 million years ago led to compression from the east and brought parts of it back above sea level. Since then it has subsided again, and most of it now lies in water 1000-3000 m deep. The 2500 metres of drill core recovered by JOIDES Resolution provide much more detail of this history and will be the subject of numerous scientific publications in the years to come.