Volcanoes Share a Hotspot But Have Mysterious Differences

In the middle of the south Atlantic Ocean, the remote island of Tristan da Cunha — named after the Portuguese explorer who discovered it in 1506 — is best known for its active volcano, which paranormal enthusiasts claim has a mysterious human-like face in its mouth. About 250 miles away, the equally remote uninhabited island of Gough also has an active volcano.

Both volcanoes are connected to the same undersea volcanic mantle plume also known as a hotspot, a pipe-like structure that transports semi-molten rock from the Earth’s interior to the sea floor. But oddly, the hot material in each of the volcanoes has a different geochemical composition, which long has puzzled scientists.

But now a team of marine scientists and volcanologists from the GEOMAR Helmholtz Centre for Ocean Research Kiel, the University of Kiel and the University of London have an explanation. Though the two volcanoes are interconnected, they’re filled with material that comes from different parts of the Earth’s mantle, an 1,800-mile-thick layer of extremely hot, dense, semi-solid rock that exists between the Earth’s crust and its core.

They’ve discovered that plume beneath the two volcanoes, which formed some 132 million years ago as the supercontinent Gondwana broke up, drew material in the early phase of its existence from another geologic structure called a Large Low Shear Velocity Province, or LLSVP, which lies roughly 1,550 miles below the Earth’s surface. (From the U.S. Geological Survey, here’s an explanation of the Earth’s interior structure.)

“In its early stages, the plume only appears to have sucked in material from the LLSVP,” GEOMAR Professor Kaj  Hoernle, the study’s lead author, explained in an article on the GEOMAR website. “But over the course of time the LLSVP material at the NW side of the margin was exhausted and material from outside the LLSVP was drawn into the base of the plume.”

Read more at Discovery News