The world's largest deep-ocean volcanic eruption in the past century, which occurred near New Zealand, is a scientific goldmine, researchers say.

The volcano, named Havre, 1000 kilometres north-west of the country's North Island, was discovered in 2002.

University of Tasmania vulcanologist and lead author of a report about the Havre volcano, Dr Rebecca Carey.

A gigantic piece of floating pumice - 400 square kilometres in size - that was found in the ocean near New Zealand in 2012 showed the eruption had occurred.

The eruption involved 14 vents, causing a massive rupture in the volcano.