A huge landmass discovered submerged underwater in the southwest Pacific should be given official recognition as a continent, scientists have claimed.

According to geologists 'Zealandia', a mostly submerged five million square km landmass off the coast of Australia and sitting partly under New Zealand, is "large and separate enough to be considered not just as a continental fragment or a microcontinent, but as an actual continent".

Arguing for 'Zealandia' to be recognised as the world's smallest continent the authors of a paper published online in the Geological Society of America's Journal claimed that although 94% of it is underwater the landmass is distinct enough to constitute a separate continent.

The 'Zealandia: Earth's Hidden Continent' paper reads: "Zealandia illustrates that the large and the obvious in natural science can be overlooked.

"Based on various lines of geological and geophysical evidence, particularly those accumulated in the last two decades, we argue that Zealandia is not a collection of partly submerged continental fragments but is a coherent 4.9 Mkm2 continent."

What do we know about Zealandia?

Believed to have broken away from Gondwana - the huge landmass that once encompassed Australia and sank 60-85 million years ago - Zealandia is roughly two-thirds the size of Australia.

It was given its name in 1995 by geophysicist Bruce Luyendyk but at the time was thought to have only three of the four prerequisites to be considered a continent.

After extensive research by geologists from the GNS Science research institute, Victoria University of Wellington in New Zealand, the Service Géologique of New Caledonia, and the University of Sydney's School of Geosciences, experts argue that 'Zealandia' has now been found to have all four necessary geological elements that justify it being given the title.

The key geographical elements 'Zealandia' possesses are an elevation above the surrounding area, a distinctive geology, a well-defined area, and a crust thicker than the regular ocean floor.