Geologists find new way volcanoes form from material in mantle's transition zone

May 16 (UPI) -- Scientists have discovered a new type of volcano formation.

While studying the planet's layers deep beneath Bermuda, scientists found evidence of volcanic material rising from the mantle's transition zone, located 250 to 400 miles beneath Earth's crust.

"We found a new way to make volcanoes," Esteban Gazel, an associate professor of earth and atmospheric sciences at Cornell University, said in a news release. "This is the first time we found a clear indication from the transition zone deep in the Earth's mantle that volcanoes can form this way."

The new research -- detailed this week in the journal Nature -- is based on the analysis of a 600-foot core sample drilled in Bermuda in 1972. For the last several decades, the massive cylinder of rock and sediment has been stored at Dalhousie University in Nova Scotia.

To figure out where the island's ancient volcanic material came from, geologists analyzed the isotopes of various trace elements, as well as the amount of water and other volatile materials trapped in the rocky layers.

Scientists were expecting to trace the ancient magma to a much deeper source. Most mantle plumes, like those fueling the Hawaiian volcanoes, rise from the core-mantle boundary.

The geochemical signals found within the core pointed elsewhere, however.

Scientists determined the now-dormant volcano that created Bermuda formed after a disturbance in the mantle's transition zone caused some volatile-rich material to begin percolating toward the surface around 30 million years ago.

The tremendous amount of water trapped inside the ancient core's crystals was the main giveaway. The mantle's transition zone holds enough water to form three oceans.

In addition to large amounts of water, scientists also found strange combinations of extreme isotopes -- isotopic signatures never seen before. But now that scientists know what a volcano derived from the mantle's transition zone looks like, they expect to find similar geochemical signatures among ancient rock layers.

"With this work we can demonstrate that the Earth's transition zone is an extreme chemical reservoir," Gazel said. "We are now just now beginning to recognize its importance in terms of global geodynamics and even volcanism."

Gazel and his colleagues are now working to determine what role this new type of volcanism played in the evolution of the planet.