Giant volcanic superstructure the size of Idaho is found beneath the Pacific Ocean


Scientists have unraveled the mystery behind how a volcanic superstructure the size of Idaho formed beneath the Pacific Ocean.

Called the Melanesian Border Plateau, a team of international researchers determined the more than 85,00-square-mile structure was created when dinosaurs ruled the Earth 145 to 66 million years ago and is still growing to this day.

Researchers used seismic data, rock samples and computer models to identify four periods of volcanic eruptions deep beneath the surface that started 100 million years ago.

The submerged structure was also found to feature rare elements used in smartphones, computers, and medical devices.

The Melanesian Border Plateau, which is larger than Idaho, is located in the South Pacific, far below the ocean's surface

The Melanesian Border Plateau, which is larger than Idaho, is located in the South Pacific, far below the ocean’s surface

In the new study, an international team of scientists led by Kevin Konrad, assistant professor of geoscience at the University of Nevada Las Vegas, assembled the available data to determine the age of the Melanesian Border Plateau.

During an oceanic expedition in 2013, Konrad and his colleagues collected samples of rock from multiple points around the Melanesian Border Plateau by dredging deep down along its slopes from aboard a ship.

Scientists have known bits and pieces of how the Melanesian Border Plateau formed, but they hadn’t been able to build a comprehensive picture until now. 

Analyzing the ages and chemical makeup of these rocks helped them put together the pieces of the puzzle.

This research is no simple task, as the water in the area can be up to 2,000 feet deep. 

The work offers a glimpse into the forces that built the Earth as we know it, and it may provide insight into what the future of our planet will look like.

Researchers used seismic data, rock samples and computer models to identify four periods of volcanic eruptions deep beneath the surface that started 100 million years ago

Researchers used seismic data, rock samples and computer models to identify four periods of volcanic eruptions deep beneath the surface that started 100 million years ago

Earth’s oceans are full of underwater volcanoes. Their eruptions formed island chains like Hawaii and Japan, as well as undersea mountains and ridges that have never pierced the ocean’s surface.

Some of the structures created by volcanic activity have built up into larger formations over time, usually in one big event at the edges of the plates that make up Earth’s crust – where two plates meet.

These boundaries between plates are known to be the sites of volcanic activity, so it makes sense that they would birth formations of igneous (volcanic) rock.

But other structures formed over time in the middle of the plates, where there is less obvious volcanic activity. This makes their origins less straightforward.

The Melanesian Border Plateau is one such structure – an oceanic mid-plate superstructure, as Konrad and his colleagues call it.

At first examination, it may look like the Melanesian Border Plateau formed from one gigantic upwelling of lava from beneath the Earth’s surface.

Such an event would have registered beyond the local area, though, sending up masses of volcanic material into the water.

‘There are some features in the Pacific basin where [scientists] have only a single sample, and it looks like a very large massive single event,’ Konrad told Live Science. ‘Sometimes when we sample these features in detail, we realize they’re actually built over multiple pulses over tens of millions of years and wouldn’t have significant environmental impacts.’  

Rather, it seems that four distinct periods of activity, all with different origins, built up the Melanesian Border Plateau over time. 

Researchers used seismic data, rock samples and computer models to identify four periods of volcanic eruptions deep beneath the surface that started 100 million years ago

Researchers used seismic data, rock samples and computer models to identify four periods of volcanic eruptions deep beneath the surface that started 100 million years ago

According to the new study, the plateau began forming from undersea volcanic activity during the Cretaceous period, between 145 and 66 million years ago – when dinosaurs still roamed the Earth. 

During this first period, a volcanic hotspot called the Louisville Hotspot burned through the lithosphere, the outermost layer of the Earth’s crust, to form a ridge and some small undersea mountains, near what would eventually become the Melanesian Border Plateau.

Hotspots form when the lithosphere passes over magma that is close to the surface.

This was just the beginning of a series of volcanic events.

Between 54.8 and 33.7 million years ago, in the Eocene epoch, some of the earliest mammals were spreading across the planet. 

At the same time, the lithosphere passed over the Rurutu-Arago hotspot, this time forming oceanic islands and underwater mountains.

The third event happened during the Miocene epoch, between 23 and 5.3 million years ago – when whales and sharks became numerous in the oceans and the first apes started walking upright.

At this time, some of the existing islands and hotspots were reactivated when the region passed over the Samoa hotspot.

‘All those same conduits that magma used to go through 45 million years ago, they’re now preexisting weaknesses that magma can start moving through 13 million years ago,’ Konrad told Live Science

The period between then and now mark the ongoing fourth pulse of the Melanesian Border Plateau’s formation.

Based on the age of lava flows identified by other researchers in the past, it seems that this most recent phase of the Melanesian Border Plateau has been caused by completely different factors than the previous three.

Deformation of the plate boundary in the Tonga Trench has led to new volcanic eruptions, which have continued to deposit rock and build it up.   

The results appeared in the January issue of Earth and Planetary Science Letters

The Melanesian Border Plateau’s complex formation may not actually be so unique, according to Konrad.

Other oceanic mid-plate superstructures probably exist, he said, especially in the South Pacific where volcanic activity continues to shape the region today.

Volcanic activity shaping the region doesn’t pose an immediate threat to people.

But better understanding it offer insights into how other undersea structures have formed. 



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