Zealandia, also known as Te Riu-a-Māui in the Māori language, is a continent that covers more than 5 million square kilometres, making it twice the size of India. Despite its immense size, 95 per cent of its area is submerged beneath the southwest Pacific Ocean, making it challenging to discover until now. Only a large mountain range (the two islands of New Zealand) and some small oceanic islands are visible on the surface. A team of geologists from around the world have recently compiled a new geological map of Zealandia using rock samples recovered from the sea and geophysical mapping methods. The map has revealed fascinating details about this previously unknown continent, including large sandstone formations and deposits of basaltic rock pebbles near its outer margins. The sandstones are estimated to be around 95 million years old and contain older granite and volcanic pebbles, suggesting that when Zealandia was above water, rivers flowing from volcanic highlands filled up tectonic basins. Geologists believe that Zealandia was gradually flooded around 40 million years ago, based on the discovery of basalt pebbles associated with underwater volcanism. The study “Reconnaissance basement geology and tectonics of North Zealandia” was published in the journal Tectonics in 2023.
