Lava Dome Surges at Mount St. Helens - KLTV.com - Tyler, Longview, Jacksonville |ETX News

1/31/05-Mount St. Helens

Lava Dome Surges at Mount St. Helens

Check out the hot glowing new growth on Mount St. Helens' lava dome, as seen from Johnston Ridge Observatory on Nov. 4. Check out the hot glowing new growth on Mount St. Helens' lava dome, as seen from Johnston Ridge Observatory on Nov. 4.
An impressive view: Mount St. Helens' crater and lava dome as seen from the north on Nov. 7. An impressive view: Mount St. Helens' crater and lava dome as seen from the north on Nov. 7.
A view of the new growth on the dome, taken on Nov. 20, compared to an FLIR (Forward Looking Infrared) image of the growth. A view of the new growth on the dome, taken on Nov. 20, compared to an FLIR (Forward Looking Infrared) image of the growth.
An aerial view of the crater and dome from the east, taken Dec. 28. An aerial view of the crater and dome from the east, taken Dec. 28.
A helicopter lands at the "Opus" area north of the new dome on Jan. 14. The camera and gas sampling station for the new dome is visible under helicopter. A helicopter lands at the "Opus" area north of the new dome on Jan. 14. The camera and gas sampling station for the new dome is visible under helicopter.

Jan. 31, 2005 -- The new lava dome at Mount St. Helens has grown more over the past three months than it did in the six years following the massive explosion of 1980 that sent volcanic ash circling the globe.

The dome is continuing to build, though geologists with the U.S. Geological Survey say its growth has slowed over the last several weeks. An "explosive type of event" that lasted for 18 minutes on Jan. 16 has added to the fascination with which scientists have been monitoring the mountain in southwestern Washington state.

"It's an incredible laboratory," said John Pallister, a geologist with the USGS' Cascades Volcano Observatory. "At the same time that as a scientist you're excited about it, you're intrigued by it and you're drawn to it, as a public employee you're always reminded of your duty not to overstate or understate any risks or dangers that it might pose."

After all the rumblings and spurts of steam at the volcano last fall, geologists say they are not sure what the dome's rapid growth means — beyond one obvious fact.

"This volcano is not sleeping — it is an active volcano," said Carolyn Bell of the USGS. "What it is going to do at this point, we don't know."

'A New Kind of Explosive Event'

The explosion that occurred earlier this month destroyed a camera and a "spider," a device used to measure the growth of the dome, that had been put in place just 36 hours earlier.

"It was a new kind of explosive event, of a kind we haven't seen since October," Pallister said. "We're keeping an eye out for more of that type of activity."

Because the explosion occurred on a cloudy day it went largely unnoticed except by those whose business it is to keep tabs on the mountain.

"If it had happened in the middle of a blue-sky day there would have been a lot more focus on it, I think," he said.

Meter-wide boulders were shot into the air by the explosion and then fell back to Earth, gouging holes in the crater floor. Ash coated much of the crater.

"It could have been caused by a pocket of gas, or it could signal a slightly different magma that has a different composition of gas, and that's what we're looking to see now," Pallister said. "If we're starting to tap something that's more gas-rich, we could see more of these types of explosions."

Before the explosion on Jan. 16, the "spider" recorded that the lava dome had grown 13 feet vertically and 23 feet horizontally in just 36 hours.

The lava dome, nicknamed the "whaleback" because of its long, oblong back, is already half the size of the dome that started after the volcano's massive eruption on May 18, 1980.

Since the events of last fall, there has continued to be low level seismic activity in the volcano, and there have been periodic releases of gas and steam, and a small amount of ash has been produced.

Though it may not fit the common idea of what a volcanic eruption is, the continued growth of the dome is just that, and how long it continues is one of the things Pallister and the others watching the mountain are curious to see.

"One of the primary questions on all our minds is as this eruption proceeds is will it run out of steam, so to speak, or tap into something containing high gas levels and lead to an explosion," Pallister said. "We don't anticipate anything like the May 18 [1980] explosion, but we don't know."

With the current state of eruption, the USGS has put the warning at Alert Level 2, the second-highest level, and warns that the action could intensify suddenly or with little warning and produce explosions like the one earlier this month or even stronger, that could cause hazardous conditions within several miles of the crater and farther downwind.

There is also a danger that small lahars — mudflows laden with volcanic debris — could suddenly descend the nearby Toutle River, if they were triggered by heavy rain or by the interaction of hot rocks with snow and ice. However, according to the latest assessment from the USGS even if there were any lahars, they do not pose much of a threat.

The primary concern is that an explosion could cause a large ash cloud that would interfere with aviation, Bell said.

It is considered extremely unlikely that even an extremely large explosion now would have the devastating effects of the 1980 blast, which blanketed parts of Washington and Oregon — including the city of Portland — in ash, left 57 people dead and between the massive landslides and the power of the blast chopped 1,314 feet off the top of the mountain.

As of Jan. 3, the new lava dome measured 44 million cubic yards, which is equivalent to 134 sports arenas, and together the area of the dome and the accompanying glacial uplift covers the space of about 60 city blocks.

The top of the new lava dome rises about 550 feet above the surface of the flanking glacier as it stood before the eruption last fall. However, geologists believe the lava dome probably extends to the base of the glacier, which means that its true height is closer to 1,100 feet.

There are many volcanoes in the Cascade range — including Mount Baker, Glacier Peak, Mount Rainier and Mount Adams in Washington State; Mount Hood, Mount Jefferson, Three Sisters, Newberry and Crater Lake in Oregon; and Medicine Lake, Mount Shasta and Lassen Peak in northern California — but Mount St. Helens is the most active.

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