New Zealand as geologists know it is many times larger than the map we recognise. The land above water is just the highest part of a crustal block extending far off the coast, mainly west and north of the North Island and east and south of the South Island.
These submarine plateaus may be as valuable to our economy as anything on or under dry land. The fishing grounds of the Chatham Rise and the gas wells off Taranaki have already contributed a great deal. There is bound to be more wealth around us.
But do we want to find it? That is a question we have to resolve. The Government has suffered two setbacks in attempts to explore the country's mineral deposits. A public outcry and protest marches greeted its proposal for prospecting in a few promising sites on the conservation estate, and last year East Cape Maori made common cause with Greenpeace to stop the Brazilian oil producer Petrobras drilling in the Raukumara Basin.
It might not be clear to all the protesters that these ventures are exploratory. There is no certainty that minerals in commercial quantities will be found and if they are, no guarantee that they can be economically extracted, and at cost that is competitive with deposits of the same mineral in other parts of the world.
Once a prospect passed all those tests the Government would then need to convince New Zealanders the value of mining would outweigh any environmental damage.
The last test could be the most difficult of all. If mere exploration can trigger the scale of protest that forced the Government to back down over conservation sites, a mining application might stand no chance. Nevertheless, we should make that decision with the best knowledge of what is down there.
The Green Party, which has led much of the opposition to "mining", held its annual conference at the weekend and seems to have adopted a more reasonable attitude to the issue. Co-leader Russel Norman said the party was not opposed to all mining, only to the extraction of coal and oil, which in its view have no future, and processes such as deep sea drilling and fracking, which it considers too risky.
Buoyed by their election result last year, the Greens are aiming to be a partner in the next Labour government. While Labour does not share the Greens' aversion to more coal mining, Dr Norman said that was a difference that could be discussed if a Labour-Greens coalition was in prospect. Hopefully deep sea drilling would be discussed in the same spirit if a well of oil or gas has been discovered by then.
New Zealand is getting a more balanced environmental law for ocean drilling. The economic benefits of extraction will be no less important than the marine ecosystem when a project is considered. The in-built environmental bias of the Resource Management Act will continue to restrict development on land and within the 12-mile jurisdiction. But the rest of New Zealand's exclusive economic zone will be easier to exploit, at least legally. Physically is another question. The Southern Ocean seabed is ridged and trenched and turbulent.
Offshore oil drilling is haunted by the accident in the Gulf of Mexico two years ago that caused one of the world's worst oil spills. The well gushed for three months while efforts were made to plug it. A rare accident such as that is a lesson for all concerned, it is not an indictment of the industry unless it happens too often.
New Zealand needs all the mineral wealth it can find. It cannot sacrifice it all for a pristine environment on land, still less beneath the sea. It is a matter of striking a reasonable balance. Ocean prospecting is expensive, internationally competitive and not often rewarded. The law should not add unnecessarily to the odds against success.