Ring of fire

The lost continent of Zealandia hides clues to the Ring of Fire’s birth. 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. 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. In 2017, geoscientists reported in GSA Today that Zealandia qualifies as a continent in its own right thanks to its structure and clear separation from Australia. 

A new analysis of chunks from Zealandia drilled from beneath the ocean floor in 2017 reveals that this continent underwent a paroxysm of change between 35 million and 50 million years ago. 

As the continental collision process known as subduction started in the Western Pacific, parts of Northern Zealandia rose by as much as 1.8 miles, and other sections dropped in elevation by a similar amount. 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. It was the birth of the  Ring of Fire, the arc of subduction zones that circles the Pacific. 

Scientists don’t know why all of the changes happened, but we now have descriptions and ideas to help us get to the bottom of what happened and why.