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Scientists operating on geologic time

• Mount St. Helens calms down, but it's still a thrill for observers

The media horde and the television satellite trucks have moved on.

What's left is a still erupting volcano, 50 miles northeast of Portland. And a few dozen geologists who continue to watch and measure and analyze Mount St. Helens, mostly from their base in Vancouver, Wash., and who are having the time of their professional lives.

'We live for eruptions, so we're enjoying it,' U.S. Geological Survey geologist Willie Scott said as he looked over digitized maps showing how much Mount St. Helens has changed even during the past couple of weeks. 'It's exciting.'

But, Scott added: 'There's a tremendous amount to do. É You get exhausted.'

Almost four months after Mount St. Helens' rumblings began, the mountain's behavior has settled into something semi-constant.

The unusual earthquakes that began under the mountain Sept. 23 led scientists based at the USGS Cascades Volcano Observatory in Vancouver to think for a while that the volcano might produce a moderate eruption.

Scientists now think it's unlikely that there will be any significant, explosive eruption. But the volcano continues what scientists call 'dome-building eruptions.' Tens of thousands of cubic feet of hot lava continue to creep into the 2,000-foot-deep crater of the volcano Ñ a crater formed by the cataclysmic landslide and eruption of Mount St. Helens in May 1980.

The new dome of hot lava that began forming in the crater in the middle of October is already about 300 feet taller than the dome that formed for six years after the 1980 eruption. It's now only about 700 feet below the rim of the crater, Scott said.

And scientists aren't sure when the eruptions and dome growth will stop.

'These kind of eruptions É can play out over literally months or years or decades,' Scott said.

But watching them is about more than scientific learning, Scott said. As the dome grows, possible hazards increase. And scientists want to be ready to warn the public.

As the dome grows, for instance, there's an increasing chance of a 'hot rock' avalanche on the dome, which could melt ice inside the crater and cause a mud flow called a lahar.

'As this gets larger and larger and larger, the danger grows and grows and grows,' Scott said.

Currently, however, scientists see no impending hazards.

And the growth of the new lava dome has slowed in recent weeks. In late October, the lava was being pushed out of the mountain at about 8 cubic meters per second, Scott said. If that rate had continued, it would have taken only 11 years to replace all of the volume of mountain displaced by the 1980 eruption, Scott said.

Now, the dome is growing 'maybe half as fast, maybe a third as fast,' Scott said.

There have been significant changes in recent days.

Just in the past week, earthquake activity underneath the mountain has declined, Scott said. While there are still almost constant very small earthquakes, a whole range of earthquake activity Ñ slightly larger quakes of roughly 1 on the Richter scale Ñ has mostly stopped. What's left are much smaller earthquakes and a few larger ones, Scott said.

'It could mean that this dome-building eruption is coming to a close, or maybe we've run through this slug of magma, or maybe it's something very brief and it's going to pick up again,' said Carolyn Driedger, a hydrologist at the Cascades Volcano Observatory.

Scott said it's part of the reality of analyzing and studying volcanoes: There's much that scientists don't know and can't predict.

'We're pretty good at short-term forecasts,' he said. 'We're not very good at long-term.'

Which is not to say that scientists don't spend hours and days, and careers, coming up with new ways to monitor and measure a volcano's activity. Advancing technology, such as the use of global positioning systems, has revolutionized volcanology since the 1980 Mount St. Helens eruption.

When USGS geologist David Johnston was killed in the 1980 eruption, he was taking measurements that can now often be done more accurately with instruments that feed data to scientists at the observatory.

Ticking away

On Monday, a helicopter pilot and a USGS scientist, battling unpredictable winds and thermal updrafts from hot lava and steam, lowered a portable contraption with a GPS device onto the new lava dome. Such devices precisely measure movement of the dome.

'So this guy, who knows how long he's going to last?' Scott said as he sat in his office at the observatory and pointed out a tiny yellow square Ñ the portable device Ñ in a recent overhead photo of the lava dome.

Two similar devices have been destroyed on the mountain Ñ possibly by falling through cracks that open on the dome, possibly by falling off the edge of the shifting dome, Scott said. There are usually about a half-dozen such devices inside the crater or on the mountain's flanks at any time, Scott said.

A rare opportunity

Dozens of other instruments are constantly taking hundreds or thousands of measurements on the mountain.

All of them underline the rare opportunity Northwest volcanologists have Ñ to study an erupting volcano.

'With each well-studied eruption, we test hypotheses and confirm them or reject them,' Scott said.

Before the current Mount St. Helens activity, geologists at the Cascades Observatory were studying volcanoes throughout the Northwest and beyond, and exploring scientific issues that had little to do with Mount St. Helens specifically. But today, Scott estimated, 90 percent of the Vancouver geologists are doing at least some work that relates to the local volcano.

'It just more intense and more collaborative É because people are focused on a single issue,' he said.

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