Visitors have gathered by the hundreds to watch Mount St. Helens blow off steam, and so far the volcano has not disappointed.
MOUNT ST. HELENS NATIONAL MONUMENT, Washington Visitors have gathered by the hundreds to watch Mount St. Helens blow off steam, and so far the volcano has not disappointed.
But the weather was about to put a damper on the show: After days of clear views of steam bursts amid mounting signs of a larger eruption, the National Weather Service was predicting mostly cloudy skies, with rain likely by Tuesday night.
Foul weather also could hamper monitoring of the volcano's vital signs, blocking visual observation and possibly the sampling of gas emissions that could be precursors to a more powerful eruption that scientists said could happen at any moment.
"Visual observations are very important," U.S. Geological Survey spokeswoman Catherine Puckett said Tuesday. "It definitely affects the ability to see if an eruption has occurred."
Monday was another field day for volcano watchers at the Coldwater Ridge Visitors Center, at 8.5 miles from the peak the closest tourists could get.
"Wow. It was amazing," said Alex Turchiano, 9. "I was hoping to see lava so I could see the trees fall down and the lava flow into the water. I wanted to see what it was going to do, whether it would stop or keep going."
The 40-minute steam burst he saw was far less dramatic. Scientists stopped short of calling it an eruption because it was almost entirely vapor, rather than fresh volcanic material.
Even in the event of a larger eruption, scientists said there was hardly any chance of a repeat of the mountain's lethal 1980 explosion or of Hawaiian-style lava flows.
The midmorning steam burst, which followed swelling in the 1,000-foot-high lava dome in the crater, rose to 10,000 feet, nearly 2,000 feet above the 8,364-foot high point on the rim. A smaller one rose over the rim in the afternoon.
Runoff from a melting glacier formed a pond about 120 feet across just south of the dome in the crater, and it was bubbling at the center, Puckett said Tuesday. New cracks were developing in much of the dome and rocks as hot as 122 degree Fahrenheit tumbled off the growing mound and into the water.
In foul weather, scientists would likely be unable to fly over the crater to sample volcanic gases as they have, but would look to earthquake monitoring devices and equipment that measures ground deformation, among other things.
Guy Medema, a seismic analyst at the University of Washington's Seismology Lab in Seattle, said earthquakes of magnitude 2 and 3 continued after the first steam burst, unlike a hiatus in seismic activity for several hours following a steam eruption Friday.
"It apparently didn't release enough stress to shut the earthquakes down," Medema said.
Scientists were expecting such bursts as superheated rock comes into contact with runoff from melting snow and ice.
"Now most of us are convinced there's fresh magma (molten rock) down there," hydrologist Carolyn Driedger said.
Since Sept. 23, thousands of tiny earthquakes have shaken the mountain, and several steam eruptions have occurred, the most seismic activity at the peak since the months following the 1980 blast.
Source: Associated Press