About 120 million years in the past, a gargantuan blob of sizzling rock indifferent from the sting of Earth’s core and oozed up towards the planet’s floor. Right this moment, an enormous chunk of that blob — or “superplume,” as geologists name it — could also be lurking off the coast of New Zealand, new analysis suggests.
In a research printed Could 27 within the journal Science Advances, researchers measured the velocity of seismic waves touring by means of a layer of Earth known as the mantle that sits between the planet’s crust and outer core. They centered on Hikurangi Plateau — an unlimited, triangle-shaped chunk of volcanic rock positioned about 2,000 miles (3,200 kilometers) beneath the highest of the South Pacific Ocean, simply off the coast of New Zealand’s North Island. The staff discovered a match between the seismic waves touring by means of that chunk and people touring by means of two different close by volcanic constructions.
In line with the research authors, it is doubtless that every one three of those underwater constructions have been as soon as a part of the identical gargantuan mega-plateau, fashioned greater than 100 million years in the past throughout the largest outpouring of volcanic materials in Earth’s historical past.
“The associated volcanic activity may have played an important role in Earth history, influencing the planet’s climate and also the evolution of life by triggering mass extinctions,” research co-author Simon Lamb, an affiliate professor at Victoria College of Wellington in New Zealand, said in a statement. “It is an intriguing thought that New Zealand now sits on top of what was once such a powerful force in the Earth.”
A lava blob legacy
In line with Stern, mantle plumes kind when enormous “lava lamp blobs” of sizzling, buoyant rock break free from the boundary the place Earth’s mantle meets the outer core, then rise 1000’s of miles up towards the floor. Whereas most of those blobs get caught within the mantle, smaller chunks proceed to rise upward, step by step melting as strain decreases and at last erupting on the floor by means of volcanoes.
Geologists suspect that mantle plumes are chargeable for among the largest volcanic hotspots on Earth, together with the Hawaiian-Emperor seamount chain, the lengthy conga line of useless and lively volcanoes stretching from the Hawaiian Islands to the Pacific coast of Russia. (The chain can also be dwelling to the only largest volcano on Earth.)
However the mantle plume that welled up underneath the South Pacific 120 million years in the past could be the world’s largest, the researchers wrote, if the fragmented plateaus it left behind are any indication. The Hikurangi Plateau close to New Zealand, for instance, covers an space of roughly 150,000 sq. miles (400,000 sq. kilometers), making the submerged construction practically twice as massive because the New Zealand mainland. If it was as soon as a part of an excellent bigger mega-plateau together with the Ontong-Java and Manihiki Plateaus, the researchers reasoned, the three constructions should share comparable rock properties, each above and beneath the seafloor.
To check that principle, the staff measured the velocity of seismic waves touring underneath Hikurangi. Utilizing information obtained from earthquakes and managed undersea explosions, the staff discovered that seismic waves traveled horizontally by means of the rocks at practically 6 miles per second (9 km/s), roughly a mile per second quicker than the typical international velocity at which seismic waves journey by means of the mantle.
Surprisingly, although, seismic waves moved rather more slowly when touring vertically upwards beneath the plateau. These velocity traits are indicative of an historic mantle superplume that has begun to break down, the researchers wrote — and that unusual relationship between vertical and horizontal wave speeds completely matched the wave speeds beneath the Ontong-Java and Manihiki Plateaus.
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In line with the researchers, these findings counsel that the three huge, volcanic plateaus within the South Pacific are certainly damaged items of 1 monumental complete, laid down by the only largest superplume ever detected on Earth. In its authentic kind, that historic mega-plateau — generally known as the Ontong-Java-Manihiki-Hikurangi Plateau — would have coated about 1% of the planet’s floor, with an space about half as massive because the continental United States, the research discovered.
“Subsequently, the movement of the tectonic plates broke up this plateau, and one fragment — right now forming the Hikurangi Plateau — drifted away to the south,” lead research writer Tim Stern, a geophysicist at Victoria College of Wellington, mentioned within the assertion.
Hopefully, Stern added, the unusual seismic wave velocity signature linking these three plateaus might be used as a “fingerprint” to determine different scattered fragments of the once-giant superplume.
Initially printed on Live Science.