Scientists say model to explain volcanoes

HONOLULU (AP) - Geophysicists in Hawaii and Texas have come up with a mathematical model that could explain a lot about Hawaii's Mauna Loa and Kilauea volcanoes.

They have been looking at how the volcanoes are linked and yet have distinct and separate eruptions.

For instance, the U.S. Geological Survey says that between 1934 and 1952, only Mauna Loa was active, but between 1952 and 1974, only Kilauea was active.

Global Positioning System data show that between 2003 and 2007, both volcanoes bulged upward due to the pressure of rising magma.

Helge Gonnermann, an assistant professor of Earth science at Rice University in Houston, said there appears to be a lag time as the pressure is transmitted slowly through partially molten material 50 miles below the Earth's crust.

"We know both volcanoes are fed by the same hot spot, and over the past decade we've observed simultaneous inflation, which we interpret to be the consequence of increased pressure of the magma source that feeds them," he said.

"In the GPS records, we first see inflation at Kilauea and then about a half a year later at Mauna Loa," Gonnermann said. "Our hypothesis is that the pressure is transmitted slowly through a partially molten and thereby porous region of the asthenosphere, which would account for the simultaneous inflation and the lag time in inflation."

Scientists do know that Kilauea and Mauna Loa must have separate channels to the source because their respective flows have slightly different chemical signatures.

Gonnermann said in an email that magma rises to the surface from beneath each volcano from a partially molten region of the mantle, through what is called the brittle lithosphere, in likely long-lived and relatively well-connected pathways and cracks.

The results of the study are in the November issue of Nature Geoscience.

[Courtesy of The Associated Press]