Study finds lava not from core of Earth

By Christie Wilson
Advertiser Neighbor Island Editor

New research on Hawaiian lava rocks has resolved a scientific controversy about whether large volcanoes are a pipeline to the Earth's core.

Findings announced last week by a team of scientists at England's University of Bristol indicate the mantle "plumes," or upwellings of molten lava, that formed Hawai'i's volcanoes do not contain any core material and are much shallower than theorized. Just how deep they are remains a mystery.

Anders Schersten at Bristol's Department of Earth Sciences said the results are important in understanding the Earth's core and its magnetic field, which affects everything from bird migration to airline navigation.

Schersten said a hot debate erupted in the past decade after other studies suggested the mantle plumes originated at the edge of the core, at a depth of about 1,864 miles. The mantle is the area between the Earth's crust and its core.

"It was also suggested that maybe these mantle plumes, especially those in Hawai'i, sucked up a bit of the core and brought it to the surface, in which case the Hawaiian volcanoes would be a highway to the center of the Earth," he said.

Since the core contains trace amounts of the rare element tungsten with isotope ratios different from anywhere else on the planet, finding evidence of the unique material in the lava rocks would confirm the connection.

The Bristol scientists developed a new, high-precision technique to identify the tungsten "fingerprint." They analyzed samples from the sea floor on the flanks of the Big Island and from South African kimberlites, rocks that bring diamonds to the surface from great depths.

No trace of the core's characteristic tungsten was found, much to the disappointment of Schersten and other researchers.

"This is the nail in the coffin for the old theory ..." he said. "We lost contact with the core."

If the lava spewing from Kilauea and other Hawaiian volcanoes did not originate near the core, Schersten said, it more likely contains material "recycled" from the mantle as a result of the subduction process, when tectonic plates collide and one plate is forced under the other.

Schersten said scientists will now turn their attention to further investigating this recycling process.

Reach Christie Wilson at cwilson@honoluluadvertiser.com or (808) 244-4880.

Correction: The edge of the Earth's core is about 1,864 miles below the surface. A previous version of this story stated an incorrect figure.