Hotspot volcanoes

Scientists discover new way volcanoes form | NSF

Geoscientists have discovered the first direct evidence that material from deep within the Earth’s mantle transition zone – a layer rich in water, crystals and molten rock – can seep to the surface to form volcanoes.

Researchers have long known that volcanoes form when tectonic plates converge or as a result of mantle plumes that rise from the core-mantle boundary to create hotspots on the Earth’s crust.

But discovering that materials from the mantle transition zone – about 250 to 400 miles below our planet’s crust – can cause volcanoes to form is new to geologists.

“We have found a new way to make volcanoes,” explains geologist Esteban Gazel from Cornell University. “This is the first time we’ve found a clear indication of the deep transition zone in the Earth’s mantle that volcanoes can form this way.”

Gazel and his colleagues published the results of their study in the May 15 issue of Nature. The research was funded by NSF’s Division of Earth Sciences and Division of Ocean Sciences.

Take the case of the island of Bermuda.

About 30 million years ago, a disturbance in the transition zone caused igneous material to rise to the surface, forming a now-dormant volcano beneath the Atlantic Ocean, then forming Bermuda. “We expected our data to show that the volcano was a mantle plume formation – an upwelling of water from the deeper mantle – much like it is in Hawaii,” Gazel said.

Scientists say the research offers a new connection between the transition zone layer and volcanoes on Earth‘s surface.