The Melanesian Border Plateau, a massive igneous rock superstructure east of the Solomon Islands in the Pacific Ocean, has puzzled scientists for its formation around 100 million years ago.
This undersea plateau, surpassing the size of Idaho, began taking shape during volcanic eruptions in the Cretaceous period (145 to 66 million years ago). Spanning 1,000 by 200 miles, it continues to grow today.
View of the Solomon Islands taken during ISS Expedition 2.
Mysterious Origin of the Melanesian Border Plateau
The study, titled "Four distinct pulses of volcanism built the Melanesian Border Plateau: Implications for oceanic mid-plate superstructure formation" published in the journal Earth and Planetary Science Letters, delves into the complex formation of the Melanesian Border Plateau, situated to the east of the Solomon Islands.
Unlike the conventional large igneous provinces, which typically form in a single magma flood, this plateau underwent a distinct evolution through four separate pulses of volcanism, each with unique root causes.
According to Kevin Konrad, the lead scientist from the University of Nevada, Las Vegas, comprehending this timeline is crucial as giant volcanic features beneath the ocean often have profound but poorly understood implications for climate and may be linked to mass extinctions.
In some instances, geological features resembling large igneous provinces are constructed over extended periods, accumulating rock layers akin to a layer cake. The challenge lies in differentiating between these and those formed in a single massive event, especially with limited rock samples.
Konrad emphasizes that detailed sampling reveals the true nature of these features, indicating whether they evolved over multiple pulses spanning tens of millions of years, without significant environmental impacts.
The analysis of rock samples collected from the undersea mountains and volcanoes forming the plateau provided insights into its gradual formation. Originating around 120 million years ago, a section known as Robbie Ridge emerged during a colossal basaltic lava flood, creating an undersea plateau that likely remained submerged.
Subsequently, 45 million years ago, the Pacific piece drifted over the Rurutu-Arago hotspot, generating an undersea mountain chain or seamount, with islands that eventually eroded. Thirteen million years later, the seamount encountered the Samoa hotspot, constructing new islands.
Over the past three million years, tectonic activities at the Tonga Trench triggered fresh volcanic eruptions on the plateau, employing a mechanism distinct from the preceding hotspot volcanism.
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Other Superstructures in the Ocean Floor May Also Exist
Unlike some regions in the Pacific basin where a single sample might give the impression of a massive, singular volcanic event, the Melanesian Border Plateau reveals a more intricate history.
Konrad highlighted the importance of detailed sampling and noted that, upon closer examination, some features turn out to be built over multiple pulses spanning tens of millions of years, lacking significant environmental impacts.
The research, involving the analysis of rock chemistry collected over the past decade, concludes that the Melanesian Border Plateau underwent several transformations while drifting over hotspots in the Earth's mantle. This process resulted in the formation of chains of underwater islands.
The discovery suggests that many other "ocean mid-plate superstructures" may exist, awaiting exploration as scientists delve deeper into the world's oceans. Konrad anticipates that increased sampling detail will reveal greater complexity in these formations.
The Ocean Exploration Trust and NOAA are sampling U.S. seamounts. Konrad and colleagues plan to study mid-Pacific mountains, suggesting the term "oceanic mid-plate superstructures."
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