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No Longer an Island

Zealandia: Our Continent Revealed
by Nick Mortimer and Hamish Campbell (Penguin, $60)
Reviewed by Simon Nathan

Z cover-001Looking back over my geological career, I realise how lucky I was to be a working scientist during the later part of the twentieth century when ideas on the nature of the Earth underwent a revolution. When I was a student in the early 1960s, the idea of continental drift was regarded by many people as laughable. Twenty years later the concept of plate tectonics was widely accepted, and it started to be appreciated that the older rocks in New Zealand were a fragment of the ancient Gondwana continent. This book is an excellent account of how New Zealand is part of  the largely submerged continent of Zealandia, now the world’s seventh continent, extending from New Caledonia in the north to Campbell Island in the south.

In reviewing this book, I should note at the outset that I know the authors, which is hardly surprising in the small geoscience community in this country. Indeed, as both of them have played a leading role in developing ideas on the nature of continental New Zealand, it would be difficult to find a reviewer who did not know them, and many of the other scientists who feature in this volume.

Zealandia and the other six continents.

Zealandia and the other six continents.

The idea that New Zealand is part of a large submerged continent is not new. Having returned from a trip to the Subantarctic islands and the Chatham Islands in 1895, geologist James Hector speculated “that New Zealand is the remnant of a mountain chain that formed the crest of a great continental area that stretched far to the south and east, and which is now submerged to a depth not much more than 2000ft” [600 metres]. But Hector’s perceptive observations were overlooked for many years as geologists concentrated on the rocks they could see on land.

There was renewed interest in the extent of offshore New Zealand from the 1970s onwards with the start of offshore drilling for oil and gas, and this was given impetus by a UN agreement which allowed countries to claim an Extended Continental Shelf (ECS). Over the last twenty years a group of scientists have pulled together bathymetric, seismic and gravity data to build up a picture of the extent of the New Zealand continental area. The name Zealandia gradually came into use in scientific circles, but this book is the first non-technical explanation of  the evidence for and extent of Zealandia.

The topic is explored comprehensively in five substantial chapters.  Chapter 1 – ‘Identity’ includes a discussion of how a continent is recognised, and the reasons why Zealandia fits the definition. Chapter 2 – ‘Discovery’ outlines the history of exploring the undersea continent, showing how the onshore and offshore evidence has been slotted together. Chapter 3 – ‘Ancestry’ shows how the continent of Zealandia came into being, including the breakup of the Gondwana supercontinent, stretching of the crust so that it is now largely submerged, and the development of the Alpine Fault separating north and south Zealandia. Chapter 4 – ‘Life’ is a fascinating account of how the distinctive fauna and flora of New Zealand came in to being. A generation ago it was believed that plants and animals were distinctive because they had evolved in isolation over the last 70 million years, but recent research is showing that many species have arrived much more recently, largely from Australia. Chapter 5 – ‘Society’ explores the consequences of humans living on the onshore part of Zealandia, including the politics of claiming a large offshore region, and the fragility of the natural environments.

The Tolkien map of Zealandia, without any sea.

The Tolkien map of Zealandia, without any sea.

This is a beautifully designed book, with colour illustrations on every page. It includes a large number of spectacular aerial obliques from all over New Zealand, taken by photographer Lloyd Homer, as well as many ground shots taken by the authors and others. The colour diagrams, many specially drawn are a special feature. Many readers will enjoy this book simply by looking at the illustrations and reading the captions. But an unfortunate note is struck by printing the captions in tiny type – clearly the designer did not understand that captions are what every reader looks at whether or not the text is read in detail.

Zealandia is smaller than  other continents, but this book presents a convincing case that it is indeed a continent. It will be interesting to see how long it takes before overseas writers recognise Zealandia as the world’s seventh continent.

Postscript

As the authors point out, the name ‘Zealandia’ was used in the past for the female personification of colonial New Zealand, a daughter of Britannia clothed in classical robes. Denis Glover gave a delightful account of this nineteenth century Zealandia in the 1966 Encyclopedia of New Zealand.