The lost continent of Zealandia hides clues to the Ring of Fire's birth

topographic map of Zealandia.
A topographic map of Zealandia, a sunken continent that includes New Zealand. (Image credit: NOAA)

The hidden undersea continent of Zealandia underwent an upheaval at the time of the birth of the Pacific Ring of Fire.

Zealandia is a chunk of continental crust next door to Australia. It's almost entirely beneath the ocean, with the exception of a few protrusions, like New Zealand and New Caledonia. But despite its undersea status, Zealandia is not made of magnesium- and iron-rich oceanic crust. Instead, it is composed of less-dense continental crust. The existence of this odd geology has been known since the 1970s, but only more recently has Zealandia been more closely explored. In 2017, geoscientists reported in the journal GSA Today that Zealandia qualifies as a continent in its own right, thanks to its structure and its clear separation from the Australian continent.

"These dramatic changes in northern Zealandia, an area about the size of India, coincided with buckling of rock layers (known as strata) and the formation of underwater volcanoes throughout the western Pacific," study co-authors Rupert Sutherland, a geophysicist at Te Herenga Waka-Victoria University of Wellington, and Gerald Dickens of Rice University in Texas, wrote in The Conversation.

It was, in a nutshell, the birth of the Ring of Fire, the arc of subduction zones that circles the Pacific. The Ring of Fire's tectonic activity is accompanied by relatively frequent earthquakes and regions of volcanic activity.

"One of the amazing things about our observations is that they reveal the early signs of the Ring of Fire were almost simultaneous throughout the western Pacific," Sutherland said in a statement.

"We don't know where or why," Sutherland said in the statement, "but something happened that locally induced movement, and when the fault started to slip, like in an earthquake, the motion rapidly spread sideways onto adjacent parts of the fault system and then around the western Pacific." 

"What were the consequences of these geographic changes for plants, animals and regional climate? Can we make a computer model of the geological processes that happened at depth? We are still figuring some of this out, but we do know the event changed the direction and speed of movement of most tectonic plates on Earth," Sutherland and Dickens wrote in The Conversation. "It was an event of truly global significance — and we now have really good observations and ideas to help us get to the bottom of what happened and why." 

Originally published on Live Science.

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Stephanie Pappas
Live Science Contributor

Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.