Deeper source of volcanic eruptions discovered

A volcanic source in large depth beneath the Earth's surface that used to be undisclosed was recently discovered.

Scientists claim that the source is located into the transition zone between the upper and lower mantle of the planet. The new perception is opposed to the conventional theory that volcanoes form within the upper mantle of Earth.

The discovery was made in the Bermuda Islands that sit on the top of a volcanic seamount (a mountain rising from the ocean seafloor that does not reach the water's surface). In particular, researchers found that material from 400-650 km beneath the Earth's surface, belonging in the transition zone (that consists of water, crystals and molten rock), can be spewed out of the region's volcanoes.

At first, the team thought the volcano's depth would be around 200-400 km, similar to that of Hawaii's volcanoes. "We were expecting our data to show the volcano was a mantle plume formation - an upwelling from the deeper mantle - just like it is in Hawaii," said geologist Esteban Gazel of Cornell University. This is the first time we found a clear indication from the transition zone deep in Earth's mantle that volcanoes can form this way," Esteban Gazel, geologist from Cornell University, stated.

Scientists utilized geological data from a core sampling conducted back in 1972. They investigated the bedrock in search of isotopes, evidence of water or specific elements. Crystals of titanium-augite, feldspars, phlogopite, spinel, perovskite and apatite were detected, indicating that the sample contained a large quantity of water. However, the finding that led to the source of lava core were the lead isotopes which were detected. Those isotopes were far too radiogenic to have originated from the upper mantle and therefore, scientists concluded that the source of the volcanoes were much deeper.

In particular, geologists found that the material derives from the transition zone and was emitted about 30 million years ago to create the aforementioned seamount. "I first suspected that Bermuda's volcanic past was special as I sampled the core and noticed the diverse textures and mineralogy preserved in the different lava flows. We quickly confirmed extreme enrichments in trace element compositions. It was exciting going over our first results ... the mysteries of Bermuda started to unfold," Sarah Mazza, geologist of the University of Münster, said.