HELENS IS GONNA BLOW

Volcano's current growth baffles experts
By Courtney Sherwood
Dec 28, 2005 - 06:21:40 am PST

Mount St. Helens has squeezed out as much hot chunky lava in the past 15 months as the volcano erupted over six years in the 1980s.

Fog, rain and clouds have kept scientists from visiting the volcano's crater since Dec. 18, but U.S. Geological Survey geologist Dave Sherrod estimated that the growing mound of fresh lava --- called a dome --- probably measures about 101 cubic yards by now.

The older lava dome on top of Mount St. Helens measures 97 million cubic yards, by contrast. It was built by a series of 22 eruptions between 1980 and 1986.

Even as the volcano pours about a dump truck load of red-hot lava onto its growing new dome every six seconds, scientists still don't know what's causing the eruption, Sherrod said.

If the lava was originating as molten rock inside the volcano, scientists would expect to see changes in the shape of Mount St. Helens, with the sides compressing in like a squeezed toothpaste tube. But that hasn't been happening.

If the molten rock was climbing up into the volcano from deep underground or near the earth's crust, scientists would expect to measure very deep seismic activity. But they can't detect that either.

By monitoring and measuring the dome, scientists hope to gain a better understanding of why Mount St. Helens is erupting and what will happen next, but their studies will be going slow until the weather improves.

"In the dead of winter we lose some of our ability to monitor the volcano the way we might like --- with visual observations and field work," Sherrod said. "It all depends on the weather, and we're anxious to get another look."

Scientists believe that lava dome eruptions allow volcanoes to rebuild their peaks, and that could eventually happen at Mount St. Helens if the current eruption continues.

As the solid chunky rocks of lava pour out of an opening inside the volcano, the dome has grown tall spines and then collapsed into a ashy gray mound a number of times since the current eruption began in October 2004. As it grows, collapses and grows, the dome is gradually getting taller.

At its current growth rate, the new lava dome could be tall enough to see over the rim of the crater by spring or summer, Sherrod said.

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