The Origins of Explosive Volcanoes May be Closer to Earth's Surface Than Expected

Where do volcanoes come from? Scientists have long thought that they erupt from deep within the interior of the planet. Now, though, researchers have announced that a layer beneath Earth's crust may be responsible for volcanic eruptions.

"For nearly 40 years there has been a debate over a theory that volcanic island chains, such as Hawaii, have been formed by the interaction between plates at the surface and plumes of hot material that rise from the core-mantle boundary nearly 1,800 miles below the Earth's surface," said Scott King, one of the researchers, in a news release. "Our paper shows that a hot layer beneath the plates may explain the origin of mid-plate volcanoes without resorting to deep conduits from halfway to the center of the Earth."

Instead of coming from deep within the interior of the planet, researchers found that eruptions originate closer to the surface, about 80 to 200 kilometers deep within the asthenosphere, which is a layer just above the Earth's mantle. Traditionally, the asthenosphere has been viewed as a passive structure that separates the moving tectonic plates from the mantle. But as the tectonic plates move several inches each year, the boundaries between the plates spawn most of the planet's volcanoes and earthquakes.

"As the Earth cools, the tectonic plates sink and displace warmer material deep within the interior of the Earth," said King. "This material rises as two broad, passive updrafts that seismologists have long recognized in their imaging of the interior of the Earth."

In fact, the hot, weak region beneath the plates acts as a lubricating layer, preventing the plates from dragging the material below along with them as they move. This layer is also the hottest part of the mantle, so there's no need for heat to be carried up to explain mid-plate volcanoes. This, in particular, shows a bit more about the origins of volcanoes and reveals a bit more about the Earth's processes.

The findings are published in the journal Science.

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