Researchers have found the first direct evidence that the material of the transition zone of the mantle can penetrate and form a volcano.
The team, including geologists from Cornell University, made the discovery by analyzing a major sample extracted from a sleeping volcano beneath the Atlantic Ocean.
"We found a new way to make volcanoes," they said
Esteban Gasel, Associate Professor at the Department of Earth and Atmospheric Sciences at Cornell University. "This is the first time we have found a clear indication of the transition zone deep in the mantle of the Earth that volcanoes can form like this."
Volcanic history of Bermuda
Before the discovery there were two events in which one volcano
is formed: when tectonic plates converge or when the mantle columns rise from the boundary between the core and the mantle to make hot spots in the crust.
Gazelle and a team expected to find evidence that the volcano was formed after the deeper rise in the mantle, just like what happened in Hawaii.
Instead, they found that 30 million years ago, a disturbance in the transition zone caused the magma to rise to the surface. The event formed a volcano in the Atlantic and ultimately gave birth to the beautiful Bermuda Island.
Sarah Matsa, from the University of Münster, Germany, and co-author of the study, analyzed the 2 600-foot main sample. It assesses the extent of isotopes, water content, trace elements and other volcanic materials.
They found that the samples contained geochemical signatures from the transition zone, including a larger amount of water enclosed in a crystal than those found in the subduction zone. The transitional zone contains three times more water than in all the oceans around the world.
"For the first time, I suspected Bermuda's volcanic past was special because I was taking a sample from the kernel and noticing the varied textures and mineralogy preserved in the various lava flows," Matsa said. "We quickly confirmed extreme enrichments in trace elements."
New way to form volcanoes
Gazel added that the findings were published in the journal Nature
, provide a new connection between the transition zone and the volcanoes on the Earth's surface.
The team also believes there will be other examples of volcanoes that are formed in a similar way.
Their next goal is to explore more places and determine the role of the transition zone of the mantle in the evolution of the planet.