Experts say Mount St. Helens moves magma like Kilauea
VANCOUVER, Wash. » Mount St. Helens might be following the example of Kilauea in Hawaii with magma being replaced from a reservoir beneath the volcano as quickly as it emerges as lava at the surface, scientists say.
While the two volcanoes are different in many respects, St. Helens appears to have become an "open system" as its dome-building eruption that began in the fall of 2004 continues at a pace that has been unchanged for the past year, said Daniel Dzurisin, a geologist at the U.S. Geological Survey's Cascades Volcano Observatory.
Analyzing digital elevation models made from high-resolution aerial photographs, scientists have kept close tabs on the rate at which lava has been pushing into the crater. At first it was about a dump truck load, roughly 8 cubic yards, per second.
A year later it was down to slightly more than 1 cubic yard per second, and since last April it has been fairly constant at about 0.6 cubic yards per second -- still the equivalent of about nine truckloads every two minutes.
The longer the eruption continues at that rate, the more likely it is that a direct pathway has developed for molten rock to emerge from deep within the planet's crust, Dzurisin said, adding that it will take another year of data to reach a more definite conclusion.
"That situation could go on for a long time," Dzurisin said. "The ongoing eruption (at Kilauea) in Hawaii, for example, started in 1983."
It took about four centuries to build the symmetrical, cone-shaped peak that led St. Helens to be compared with Mount Fuji in Japan before a massive blast on May 18, 1980, removed the top 1,314 feet, flattened miles of southwestern Washington forests and left 57 people dead.
"We know that St. Helens is capable of dome eruptions lasting decades," Dzurisin said.