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Mount St. Helens Huffs And Puffs

Mount St. Helens blew off steam again on Tuesday in what scientists said was the latest indication that a larger eruption may be in the works.

The mountain has been venting steam daily amid a series of small eruptions and volcanic tremors since Friday.

Jake Lowenstern with the Cascades Volcano Observatory in Vancouver, Washington, said there appears to be a significant amount of ash in the billowing cloud.

Scientists have said a larger eruption is likely, but there was hardly any chance of a repeat of the mountain's lethal 1980 explosion, which killed 57 people and coated much of the Northwest with ash.

Scientists stopped short of calling Monday's 40-minute steam burst an eruption because it was almost entirely vapor rather than fresh volcanic material.

The 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, U.S. Geological Survey spokeswoman Catherine 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.

Scientists were expecting steam 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.

Officials had worried that bad weather at the mountain could limit scientists' ability to monitor the volcano's vital signs, blocking visual observation and possibly the sampling of gas emissions. But Tuesday again brought bright blue skies.

Mount St. Helens blew off a spectacular cloud of steam and ash on Tuesday, the biggest plume yet in days of rumblings and the latest indication that a larger eruption may be in the works.

Tuesday's burst sent a roiling, dark gray cloud 12,000 to 13,000 feet above the mountain before it streamed several miles to the northeast.

U.S. Geological Survey vulcanologist Jake Lowenstern said the plume had "a significant amount of ash in it" but posed no immediate danger to humans or property as it rose rapidly above the 8,364-foot rim of the mountain.

"It's a fairly rural area that it's going to pass over," Lowenstern said.

The mountain has been venting steam daily since Friday amid a series of small earthquakes and volcanic tremors.

Officials at the Coldwater Ridge Visitors Center, 8½ miles north of the mountain, were warned that the latest emission could include ash. Forest Service Ranger Scott Hinderman told the several dozen people at the center's parking lot not to drive if the plume reached them.

"If ash starts falling we're going to pull everybody inside the visitors center," he said.

Scientists have said a larger eruption is likely, but there was hardly any chance of a repeat of the mountain's lethal 1980 explosion, which killed 57 people and coated much of the Northwest with ash.

Earthquakes below magnitude 3 continued into Tuesday morning, and the 1,000-foot-high lava dome within the crater had swelled by about 150 feet. Geologists believe magma beneath the crater is pushing it upward.

"It is growing a lot," said U.S. Geological Survey spokeswoman Catherine Puckett. "It is growing very rapidly."

Monday's 40-minute steam burst was almost entirely vapor rather than fresh volcanic material. Scientists were expecting steam 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.

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.

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.

Officials had worried that bad weather at the mountain could limit scientists' ability to monitor the volcano's vital signs, blocking visual observation and possibly the sampling of gas emissions. But Tuesday again brought bright blue skies.

The steam bursts provide demonstrations of Mount St. Helens' volcanic power, reports CBS News Correspondent John Blackstone.

There's still no big eruption, but scientists are pleased by every rumble the mountain makes.

"There's a lot to be learned and every time this thing shakes and spits, we learn a little more," said U.S. Geological Survey geologist Carl Thornber. "It is very likely to erupt again within the next day or two, or perhaps within the next hour or two. "

"It's very obvious from the amount of inflation that's gone on in the crater floor and adjacent to the back side of the dome, there's a lot of pressure build-up within the system and that's a large volume of material that's been pushed up," he said.

Monday was another field day for volcano watchers at the Coldwater Ridge Visitors Center, at 8½ 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."

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