Earth's Hidden Eighth Continent

 From Popular Mechanics:

Zealandia’s history is quite closely tied to the ancient supercontinent of Gondwana, which broke up hundreds of millions of years ago. Zealandia followed suit—roughly 80 million years ago, according to the latest theory. But unlike neighboring Australia or much of Antarctica, Zealandia largely sunk, leaving only a small portion of what many geologists believe should still be dubbed the eighth continent. New Zealand makes up the most recognizable above-water portion of Zealandia, although a few other islands in the vicinity are also part of the maybe-continent in question.

The latest research, led by Nick Mortimer, dredged the northern two-thirds of the submerged area, pulling up pebbly and cobbley sandstone, fine-grain sandstone, mudstone, bioclastic limestone, and basaltic lava from a variety of time periods. By dating the rocks and interpreting magnetic anomalies, the researchers wrote, they were able to map the major geological units across North Zealandia. “This work completes offshore reconnaissance geological mapping of the entire Zealandia continent,” they said. (Read more.)