For decades, geography books taught us that the world was divided into six continents. In 2017, the scientific community made official the existence of a new “intruder” of colossal dimensions: Zealandia. With an extension of 4.9 million square kilometers —equivalent to the entire European Union—, this mass of continental crust separated from Australia and Antarctica about 80 million years ago.
What makes Zealandia an absolute anomaly is not just its size, but how well it has been hidden. Unlike the rest of the continents, 94% of its body is sunk under the Pacific. Only its highest peaks manage to show their heads, forming what we step on today such as New Zealand and New Caledonia. This geographical timidity kept it as a “ghost continent” until technology allowed us, finally, to pierce the abyss.
The mission to rescue the past from the abyss. Everything changed in the summer of 2017. Expedition 371 of the International Ocean Discovery Program (IODP) It was not a pleasure cruise: the ship JOIDES Resolution set sail with a mission almost surgical. For two months, 32 scientists worked piecework, in 24-hour shifts, to extract “witnesses” from the seabed: cylinders of rock and sediment recovered almost five kilometers deep.
These sediment cores are not just mud and stone. They are, in the words of paleontologist Laia Alegret, in statements collected by The Conversation, authentic “libraries of climate history”. The findings were surprising, despite being under the sea today, the scientists found pollen from land plants and spores, in addition to thousands of microfossils of organisms They only live in very warm and shallow waters. This confirmed that Zealandia was not always an underwater world, but had periods of land covered in vegetation.
The “mirror” of future climate change. The relevance of Zealandia goes far beyond a geological curiosity. According to researchers from Rice Universitythis submerged continent constitutes a “critical region” for climate science, precisely because it is one of the places where current climate models show the greatest deficiencies. If models fail to accurately reproduce Zealand’s past climate, they warn, their predictions of future global warming may be incomplete or biased.
The focus of attention is placed especially on the Eocene, between 53 and 41 million years ago, a time in which the Earth functioned as a true “greenhouse planet”. Carbon dioxide concentrations were much higher than today and there were no permanent polar caps. Studying this period in Zealand allows scientists to “look back at our future,” offering a glimpse of how the planet will respond to conditions extreme greenhouse effect greenhouse effects similar to those we could achieve in the coming centuries.
One of the hottest spots. One of the most disturbing findings was the identification of episodes of rapid warming—rapid in geological terms, that is, on scales of thousands of years—during which ocean currents changed unexpectedly. The sediments reveal the arrival of deep water masses originating near Antarctica, a phenomenon difficult to explain in a warm world without permanent ice. This discovery, underlined by The Conversationchallenges the current understanding of how heat is redistributed in the oceans and forces us to rethink some basic assumptions of global ocean circulation.
The violent birth in the “Ring of Fire.” Zealand’s history is one of a geological “roller coaster” driven by plate tectonics. According to the results published by the expedition directorsRupert Sutherland and Gerald Dickens, the continent was sculpted by two major tectonic events:
- The Great Divorce: First, it was torn from Australia and Antarctica 85 million years ago, stretching and thinning until it sank.
- The Resurrection of Subduction: About 50 million years ago, something “globally significant” happened. What scientists call a “massive subduction rupture” began, giving rise to the Pacific Ring of Fire.
In simplified terms, this process caused huge portions of the seafloor to curve, parts of Zealand to temporarily rise above sea level, and then the continent to sink back more than a kilometer to its current configuration. It was not a local phenomenon. These tectonic forces altered the direction and speed of movement of many tectonic plates across the planet, in one of the largest geodynamic readjustments of the last 80 million years.
Microfossils and the response of life. To reconstruct these movements with surgical precision, scientists they rely on benthic foraminifera. These single-celled shelled organisms are “diagnostics of the deep.” By analyzing its remains in the ship’s laboratories, researchers can determine whether a rock stratum belonged to a shallow beach or an abyssal plain.
Furthermore, complementary technical studies, such as those presented in Paleoceanography and Paleoclimatology and marine Micropaleontologyanalyze the biotic response to hyperthermals (peaks of extreme heat). The results indicate that marine life does not react uniformly: the magnitude and speed of warming determine whether ecosystems adapt, reorganize or become stressed. These data are essential to improve predictive models of current climate change.
A sea of discoveries at risk. Zealandia’s exploration has shown that continents remain to be discovered and that the ocean floor holds the answers to the most pressing questions about our climate survival. However, science depends not only on curiosity, but on investment.
Despite the scientific success of the 2017 expedition, there are countries that later do not intervene adequately due to lack of payments. This leaves future expeditions in the air that could continue to unravel the mysteries of this seventh submerged continent, a territory that, although hidden under thousands of meters of water, has a lot to say about the air we will breathe tomorrow.
Image | Unsplash and World Data Center for Geophysics & Marine Geology
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