New Zealand represents Earth's eighth continent

Feb. 17 (UPI) -- According to new geophysical data, the islands of New Zealand are what's left of a sunken eighth continent.

Scientists say the newly identified continent -- dubbed Zealandia -- comprises nearly 2 million square miles, most of it hidden beneath the ocean surface. Its visible portions include New Zealand and New Caledonia.

"If you could pull the plug on the world's oceans, then Zealandia would probably long ago have been recognized as a continent," Nick Mortimer, a geologist at GNS Science in Dunedin, New Zealand, told Nature.

Unlike a new chemical, species or planet, there isn't an international body operating as gatekeepers to the continental club. Scientists must simply make a compelling enough case to convince a majority of their peers.

Their evidence relies on gravitational force field maps composed by satellite surveys. The maps reveal a cohesive geophysical entity, separate from the surrounding seafloor and neighboring continents.

Zealandia seafloor samples recall the composition of continental crust and are free of the dark volcanic rocks characteristic of oceanic plateaus and mid-ocean valleys.

Some scientists say whether Zealandia is termed a continent or not is irrelevant. There is no agreed-upon definition for what constitutes a continent.

"One of the main benefits of this article is that it draws attention to the arbitrary and inconsistent use of such a fundamental term as continent," said Brendan Murphy, a geologist at St. Francis Xavier University in Canada.

However, the findings -- detailed in the journal GSA Today -- are likely to shape how scientists understand the evolution of plants and animals endemic to New Zealand.