Zealandia, often regarded as Earth’s hidden eighth continent, has been the subject of recent exploration and mapping, shedding light on this submerged landmass’s geological history.
While approximately 95 percent of Zealandia lies beneath the ocean, researchers have made significant progress in documenting the northern two-thirds of this vast landmass, covering nearly two million square miles. Their efforts, detailed in a study published in Tectonics, involved dredging rock samples from the Fairway Ridge to the Coral Sea, allowing for a better understanding of Zealandia’s underwater composition.
Zealandia’s geological history is closely linked to the ancient supercontinent of Gondwana, which fragmented hundreds of millions of years ago. Zealandia itself underwent a similar process approximately 80 million years ago. Unlike neighboring Australia and much of Antarctica, Zealandia largely submerged, leaving only a fraction of what many geologists argue should be considered the Earth’s eighth continent.
New Zealand constitutes the most recognizable portion of Zealandia above water, with a few other nearby islands also being part of this submerged landmass.
The recent research, led by Nick Mortimer, focused on the northern two-thirds of Zealandia and involved extracting rock samples representing various geological time periods, including pebbly and cobbley sandstone, fine-grain sandstone, mudstone, bioclastic limestone, and basaltic lava. Through rock dating and magnetic anomaly interpretation, the researchers were able to map the major geological units across North Zealandia, thus completing offshore reconnaissance geological mapping of the entire continent.
Some of the notable findings include sandstone dating back to around 95 million years ago during the Late Cretaceous period, a mix of granite and volcanic pebbles dating back up to 130 million years during the Early Cretaceous period, and basaltic lava from about 40 million years ago during the Eocene period.
The paper also discusses how internal deformation in Zealandia and West Antarctica led to stretching, causing the plates to crack and form the Tasman Sea. Subsequent stretching further thinned Zealandia’s continental crust until it broke apart, contributing to its largely submerged status. This differs from the previously held theory of a strike-slip breakup.
Despite being largely underwater, Zealandia remains a geological marvel, with its unique history and composition fascinating scientists and researchers.
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