From: LiveScience
Published October 26, 2009 10:53 AM

Massive Pool of Magma May Feed Three Washington Volcanoes

A new study suggests there's a vast pool of magma beneath southwestern Washington State that supplies Mount St. Helens, Mount Rainier and Mount Adams. The study was published yesterday in the journal Nature Geoscience, hints that the setup could be akin to the known supervolcano at Yellowstone.

"If confirmed by additional methods, this could be one of most widespread magma-bearing areas of continental crust discovered thus far," the journal concludes in a summary of the research, led by Graham Hill of GNS Science in New Zealand.

Hill and colleagues measured the electrical conductivity in the rocks under the northern Cascade Mountain range, where the three mountains sit. Their data confirmed previous hints that there is a widespread layer of material with low conductivity below the range. They also found that narrow fingers of this material rise towards the surface, below the Mount St. Helens and Adams volcanoes.

Molten rock has a lower electrical conductivity than solid rock, so the researchers suggest there is a zone of partially molten rock that has pooled in the continental crust. According to Hill and colleagues, the small fingers probably indicate areas where the molten rock is moving up towards the magma chambers of the volcanoes, feeding future volcanic activity.

"Their interpretation is open to disagreement," Seth Moran , a volcano seismologist with the USGS Cascades Volcano Observatory in Vancouver, Wash, is quoted by McClatchy Newspapers. "Other geophysical studies don't support this theory."

Researchers have long predicted that the Yellowstone supervolcano will eventually erupt again, with devastating consequences for much of the United States. Half the country could be covered in ash up to 3 feet (1 meter) deep, one study predicts. But those same researchers say nothing suggests such an eruption is imminent. They point out, however, that Yellowstone seems to blow its top about every 600,000 years.

Separately, in a study last month, fossilized remains of a supervolcano that erupted some 280 million years ago in the Italian Alps are giving geologists a first-time glimpse at the deep "plumbing system" that brings molten rock from far underground to the Earth's surface.