Mount St. Helens still an exciting study subject

One year after Mount St. Helens awoke from its slumber, the volcano that is slowly rebuilding itself is still generating excitement and wonder among the scientists who study it.

At a briefing Friday to celebrate the one-year anniversary of an intense swarm of earthquakes that signaled the volcano’s reawakening after 18 years of relative quiet, scientists with the U.S. Geological Survey at the Cascades Volcano Laboratory in Vancouver, Wash., shared what they’ve learned so far – at the news conference and via teleconferencing.

The volcano has been spitting out magma at a slow, steady pace ever since the molten rock first flowed to the surface last October, and there’s no sign this buildup will stop or become explosive any time soon.

This is true, in part, because of something scientists have learned about the magma oozing from the volcano. It contains much smaller amounts of explosive gas than magma from the 1980 Mount St. Helens eruption that killed 57 people and sent a river of hot mud and ash down the Toutle River Valley.

The current magma flow’s continuous upward movement may also be easing pressure that could otherwise contribute to a new, more explosive eruption.

Although things could change at any time, scientists are not expecting any big changes at Mount St. Helens in the near future.

Just in case something does change, however, geologist Dan Dzurisin, 53, who has studied the volcano after each of the developments since 1980, said he’s not making any retirement plans.

He said the current eruption could last months, years or even decades longer.

The new lava dome is growing about six times faster than it did during the six years of dome building between 1980 and 1986. The extrusion rate is about 1.3 to 9.2 cubic yards per second, averaging 3 cubic yards – enough to fill up the back of a pickup truck every second.

The new Mount St. Helens dome was about 10 feet below the rim of the crater in July, although it has crumbled a little since then. The growth has been in a series of six big upward thrusts or “whalebacks” as the scientists like to call them because of their shape. At the rate it is growing, Mount St. Helens could regain its conical top within decades.

Though plumes of steam, rocks and dirt continue to rise above the crater on a regular basis, Dzurisin said what’s happening away from tourists’ view is more exciting.

“Every opportunity to study an active volcano is a rare and important one,” he said. “The more we understand about the volcano, the better job we’re going to do keeping the natural process from becoming a natural disaster.”

He said scientists have been surprised that the magma and rock pushing up through the crater has mangled but not melted the glacier that has grown in crater since 1980. They estimate the glacier has shrunk by as much as 25 percent, but they cannot be positive because the melted ice is flowing into groundwater, not nearby streams.

Chemical analysis has proven false an initial assumption that the lava coming to the surface this past year was left over from the 1980 eruption. A workshop of 25 scientists from around the country discovered this past summer that some new lava seems to be mixed in with the old, Dzurisin said.

Scientists have also been surprised to learn how quickly Mount St. Helens can turn back on – from the signal quakes to red-hot lava at the surface in a few weeks.

They still don’t know what triggered the 2004 eruption and they are working to understand many other aspects of what’s been happening at Mount St. Helens over the past year.

For example, they don’t know why the current eruption has lasted so long and they haven’t figured out what relationship exists between the swarms of shallow earthquakes and the lava flow, which comes from miles deeper in the earth.

Continuous scientific oversight will add to their understanding of this young volcano, while also helping to make sure any new developments are carefully monitored.

“We’re confident the volcano would give us a warning of a major change,” Dzurisin said. “Before potentially explosive magma reaches the surface, we expect to have warning. … That’s our answer and we’re sticking to it.”