进行注册
登入Natural disaster - Volcanic eruption
2 post(s)
-
-
Alaska braces for possible volcanic eruption
Thu Dec 22, 2005 9:14 PM ET
By Yereth Rosen
ANCHORAGE, Alaska (Reuters) - A restless volcano near Alaska's most populated region is being watched by scientist and officials, who warned on Thursday of the risk of clouds of ash and a tsunami from a possible eruption.
The intensifying rumblings in the past few weeks at Augustine Volcano, an island peak 175 miles southwest of Anchorage in Cook Inlet, have produced a series of steam explosions, releases of sulfur gas and signs that there may be an eruption similar to events in 1986 and 1976 which sent ash clouds as high as 40,000 feet, scientists said.
There has even been an increase of 1 inch at the top of the 4,134-foot (1,260-m) volcano, a sign that seismic activity is causing the summit to bulge slightly, said John Power, a seismologist with the Alaska Volcano Observatory, a joint office run by the U.S. Geological Survey and state agencies.
"All of these things are very typical of what you would expect to see in a volcano that is reawakening," Power said.
Although there are no specific signs that an eruption is imminent, flight restrictions are already in place and there are plans to expand those if activity increases at the volcano.
If Augustine does erupt, that could result in grounded flights, school closures and even evacuations, officials said. It is also possible that there will be a landslide from the volcano into the waters of Cook Inlet, causing a tsunami, they said.
Such an event occurred in 1883, when a wave believed to be 20 feet high hit the Native Alutiiq village of Nanwalek, 50 miles east of Augustine.
"Any time you have a volcano on the water that's erupting, common sense says you could have a flank collapse and a wave," said Paul Whitmore, director of the West Coast/Alaska Tsunami Warning Center.
Anchorage is too far away to be at risk from an Augustine-related tsunami, Whitmore added.
But preparations for the possibility are well under way in Nanwalek, said Sergie Active, rector of the local Russian Orthodox church in the village of 200 people.
"We would have to go to higher ground, basically. The first thing is to have things packed away, just in case," Active said in a telephone interview from the local tribal council office.
"We have asked all the households to have sleeping bags, clothes, food, first-aid kits -- all the things that would be needed."
Augustine is one of Alaska's most active volcanoes, with five eruptive periods since the late 1800s, scientists said. Those events have generally started with major ash explosions that last a few days, followed by months of less powerful eruptions that produce oozing lava at the summit, they said.
-
-
-
Volcano's current growth baffles experts
By Courtney Sherwood
Dec 28, 2005 - 06:21:40 am PST
Mount St. Helens has squeezed out as much hot chunky lava in the past 15 months as the volcano erupted over six years in the 1980s.
Fog, rain and clouds have kept scientists from visiting the volcano's crater since Dec. 18, but U.S. Geological Survey geologist Dave Sherrod estimated that the growing mound of fresh lava --- called a dome --- probably measures about 101 cubic yards by now.
The older lava dome on top of Mount St. Helens measures 97 million cubic yards, by contrast. It was built by a series of 22 eruptions between 1980 and 1986.
Even as the volcano pours about a dump truck load of red-hot lava onto its growing new dome every six seconds, scientists still don't know what's causing the eruption, Sherrod said.
If the lava was originating as molten rock inside the volcano, scientists would expect to see changes in the shape of Mount St. Helens, with the sides compressing in like a squeezed toothpaste tube. But that hasn't been happening.
If the molten rock was climbing up into the volcano from deep underground or near the earth's crust, scientists would expect to measure very deep seismic activity. But they can't detect that either.
By monitoring and measuring the dome, scientists hope to gain a better understanding of why Mount St. Helens is erupting and what will happen next, but their studies will be going slow until the weather improves.
"In the dead of winter we lose some of our ability to monitor the volcano the way we might like --- with visual observations and field work," Sherrod said. "It all depends on the weather, and we're anxious to get another look."
Scientists believe that lava dome eruptions allow volcanoes to rebuild their peaks, and that could eventually happen at Mount St. Helens if the current eruption continues.
As the solid chunky rocks of lava pour out of an opening inside the volcano, the dome has grown tall spines and then collapsed into a ashy gray mound a number of times since the current eruption began in October 2004. As it grows, collapses and grows, the dome is gradually getting taller.
At its current growth rate, the new lava dome could be tall enough to see over the rim of the crater by spring or summer, Sherrod said.
-
