Saturday, January 26, 2008
Antartica is spread out over an active volcano
The researchers from the British Antarctic Survey, in findings published in the February edition of the journal Nature Geosciences, report the Hudson Mountains subglacial volcano erupted about 2,200 years ago.
"We believe this was the biggest eruption in Antarctica during the last 10,000 years," said lead author Hugh Corr in a release. "It blew a substantial hole in the ice sheet and generated a plume of ash and gas that rose around 12 km into air."
This ash and gas eventually fell back to the ice surface and was buried by years of snow, the team reports, creating a bright reflection in the ice over an elliptical area of about 23,000 km square.
Previous studies had misidentified the reflective area as the ice bottom. The researchers discovered this ash layer by analyzing radar data collected during an airborne survey of the area in 2004-05.
Additionally, ice cores extracted from the area showed a thin layer of ice that conducts electricity unusually well. The team said this conductivity may be a result from the volcano blasting acid and other conductive chemicals into the air that subsequently fell to the ground and became incorporated into the ice.
The thickness of the ice above the ash layer suggests the eruption occurred 2,200 years ago, most likely around 325 BC, the report said.
The researchers have no direct evidence of recent eruptive activity, but believe the volcano is still active. Evidence of recent activity includes a report of steam in the area in 1974 and an eruption reportedly seen in satellite data in 1985.
An active volcano in the area could generate heat under the ice and accelerate the melting of the nearby Pine Island glacier, the report said. As well, the heat would create melt-water to lubricate the glacier's movement.
"The flow of this glacier towards the coast has speeded up in recent decades and it may be possible that heat from the volcano has caused some of that acceleration," said Prof. David Vaughan, another study author, in a release.
However, he adds, the heat from the Hudson Mountains subglacial volcano would probably not affect neighbouring glaciers.
"It cannot explain the more widespread thinning of West Antarctic glaciers that together are contributing nearly 0.2 mm per year to sea-level rise," Vaughan said. "This wider change most probably has its origin in warming ocean waters."
The team said the finding may help researchers refine their predictions on rising sea levels and the future of the ice sheet.
Over 50 were rescued from Chile's volcano eruption
There were no reports of injuries or damage, but dozens of tourists were evacuated from the base of the Llaima volcano after it erupted on Tuesday evening .
The 54 people rescued had been stranded overnight after a local river swelled with meltwater and cut off road access.
"Army personnel evacuated 43 people this morning who remained in the Conguillio National Park. Another 11 people, park personnel and their family members, were also evacuated," the National Emergency Office said in a statement.
The volcano was calmer by Wednesday afternoon but Chile's deputy interior minister Felipe Harboe said further eruptions were possible.
"At this moment I would recommend against tourism in the area," said Carmen Fernandez, the emergency agency's director.
The eruptions on Tuesday sent lava spewing down the 10,253-foot (3,125-meter) volcano's east side and shot a column of ash and smoke into the air that forced air traffic to be diverted in neighboring Argentina.
Chile's geological service said abnormal seismic activity had also been registered around another volcano, Puyehue, to the south of Llaima.
Military ground vehicles had to be used in the rescue around LLaima because heavy fog prevented the use of helicopters.
The surrounding Conguillio National Park, about 50 miles from the city of Temuco, was closed off to visitors on Wednesday and authorities told curious tourists not to get too close.
Llaima is one of Chile's most active volcanoes and is in the Araucania region in southern Chile, about 435 miles (700 km) south of the capital Santiago.
Before the eruption, people in the towns closest to the volcano said they heard loud underground noises.
Chile is home to the world's second largest and second most active chain of volcanoes, after Indonesia.
Sunday, January 20, 2008
An active volcano underneath West Antartica
The explosive event -- rated 'severe' to 'cataclysmic' on an international scale of volcanic force -- punched a massive breach in the icesheet and spat out a plume some 12,000 metres (eight miles) into the sky, they calculate.
Most of Antarctica is seismically stable. But its western part lies on a rift in Earth's crust that gives rise to occasional volcanism and geothermal heat, occurring on the Antarctic coastal margins.
This is the first evidence for an eruption under the ice sheet itself -- the slab of frozen water, hundreds of metres (feet) thick in places, that holds most of the world's stock of fresh water.
Reporting in the journal Nature Geoscience, the investigators from the British Antarctic Survey (BAS) describe the finding as 'unique.'
It extends the range of known volcanism in Antarctica by some 500 kilometres (300 miles) and raises the question whether this or other sub-glacial volcanoes may have melted so much ice that global sea levels were affected, they say.
The volcano, located in the Hudson Mountains, blew around 207 BC, plus or minus 240 years, according to their paper.
Evidence for this comes from a British-American airborne geophysical survey in 2004-5 that used radar to delve deep under the ice sheet to map the terrain beneath.
Vaughan's team spotted anomalous radar reflections over 23,000 square kilometres (8,900 sq. miles), an area bigger than Wales.
They interpret this signal as being a thick layer of ash, rock and glass, formed from fused silica, that the volcano spewed out in its fury.
The amount of material -- 0.31 cubic kilometres (0.07 cubic miles) -- indicates an eruption of between three and four on a yardstick called the Volcanic Explosive Index (VEI).
By comparison, the eruption of Mount St. Helens in 1980, which was greater, rates a VEI of five, and that of Mount Pinatubo in 1991 is a VEI of six.
'We believe this was the biggest eruption in Antarctica during the last 10,000 years,' BAS' Hugh Corr says.
'It blew a substantial hole in the icesheet and generated a plume of ash and gas that rose around 12 kms (eight miles) into the air.'
The eruption occurred close to the massive Pine Island Glacier, an area where movement of glacial ice towards the sea has been accelerating alarmingly in recent decades.
'It may be possible that heat from the volcano has caused some of that acceleration,' says BAS professor David Vaughan, who stresses though that global warming is by far the greater likelier cause.
Volcanic heat 'cannot explain the more widespread thinning of West Antarctic glaciers that together are contributing nearly 0.2mm (0.008 of an inch) per year to sea-level rise,' he adds.
'This wider change most probably has its origin in warming ocean waters.'
Approximately 8,000 villagers evacuate as Colombian volcano erupts
This video frame released by the Colombian Institute of Geology and Mining shows the eruption.
Images broadcast on Caracol, a Colombian television station, showed white smoke pouring into the evening sky from a mountain with a summit of 14,029 feet (4,276 meters).
Authorities canceled Friday classes in schools around the Galeras volcano, Caracol reported.
The Galeras volcano is one of the most active in Colombia.
The Volcanic Ash Advisory Center in Washington, which tracks eruptions in a region that includes Colombia, said early Friday that an "explosive eruption" had taken place.
Fernando Gil, director of Colombia's Seismological Network, told The Associated Press by phone it was the volcano's most severe eruption since it reactivated in 1989.
"Depending on the wind direction it's going to spread ashes over the entire area," he told the AP, adding that "most of [Galeras'] eruptions are violent and short."
Activity at the volcano also prompted an evacuation in November 2005, and a 1993 eruption killed a group of scientists working nearby.
Mount St.Helen's volcano is blowing steam!
Pallister, a private pilot who works in the hazards section of the U.S. Geological Survey's Cascades Volcano Observatory, noticed a line of steam coming from a zipper-like fracture line atop the growing lava dome in the crater of the southwest Washington volcano.
"It was interesting enough to take some pictures," Pallister told The Columbian newspaper of the Sunday flight.
After landing, he learned that a 2.9-magnitude earthquake had registered on seismographs at the observatory in Vancouver. That was followed by a small tremor that lasted nearly an hour and a half, an unusually long period, punctuated by a second quake of 2.7 magnitude - all in the same period in which he saw the steam.
Along with the shake, rattle and roll, tiltmeters registered alternate ground swelling and deflation near the lava dome, which has been growing in the crater since the fall of 2004.
All are typical signs that magma, superheated gases or both are moving through conduits beneath St. Helens, which blew its top with devastating force on May 18, 1980, leveling 230 square miles of forest and killing 57 people.
The last noteworthy tremor at the volcano lasted 55 minutes on Oct. 2, 2004, and was much more powerful, registering on seismometers from Bend, Ore., to Bellingham and causing a hasty evacuation of the Johnston Ridge Observatory five miles north of the crater.
No evacuations have been ordered this time - seismic activity had slowed down since the episode Sunday and the likelihood of a major eruption seemed low. Hydrologist Carolyn Driedger said Wednesday that scientists were taking advantage of some clear weather to check on the equipment that monitors the volcano 24 hours a day and make some minor repairs.
Cynthia A. Gardner, scientist in charge of the volcano observatory, said that scientists had quit venturing into the crater. The equipment checks are being done on the flanks of the crater, outside the area where the new dome is growing.
"We're just being cautious. It's not that we're anticipating any activity," Gardner said Wednesday.
She said the precise cause of the recent activity was not entirely clear.
"The settling of the growing lava dome might have caused some fracturing and might have changed the subsurface openings so that water was either being squeezed out of openings or opening new areas," Gardner said Tuesday.
The last precise measurements, drawn from images in July, indicated the latest eruptive phase has pumped 123 million cubic yards of material into the crater. The rate has slowed considerably, but the episode Sunday showed that could change at any time, Pallister said.
"Rumors of an early end of this eruption are once again shown not to be the case," he said. "It's still got some surprises."
Saturday, January 19, 2008
Ecuador: Villagers leave volcano slopes!
She said that could mean pyroclastic flows blasts of volcanic material «that descend at high speeds and burn everything in their way.Tungurahua, which has been active since 1999, has been freeing a high level of energy since Dec. 22, Mothes told The Associated Press in a telephone interview.«We have indications that there may be important volumes of magma which would be liberated in an eruption,» she said.
Juan Salazar, the mayor of Penipe, one of 10 villages evacuated last week from the western slopes of Tungurahua as precautionary measure, said 1,200 hectares (3,000 acres) of crops and pastureland have been damaged by ash from the volcano.There have been no lava flows since the volcano began spitting out ash in December, he said.
Villagers return by day to tend to their crops and farm animals but stay in temporary shelters outside the danger zone at night.Salazar said the government had decided to provide new houses for 286 families that cannot return to their homes at night. He said the families would receive the keys to the houses on Feb. 9 along with small plots for growing crops.
Salazar said the families «should never again sleep in the danger zone.Tungurahua erupted in July and August of 2006, causing at least four deaths. The eruptions forced the evacuation of thousands of villagers and damaged thousands of hectares (acres) of crops buried under tons of ashes and lava flows.
Saturday, January 12, 2008
Volcano eruption is likely to happen soon in Ecuador
Patricia Mothes, a U.S. expert on volcanoes, said the 16,575-foot volcano, located 80 miles southeast of Quito, "is preparing to generate, in days or weeks, a great eruption."
She said that could mean pyroclastic flows - blasts of volcanic material "that descend at high speeds and burn everything in their way."
Tungurahua, which has been active since 1999, has been freeing a high level of energy since Dec. 22, Mothes told The Associated Press by telephone.
"We have indications that there may be important volumes of magma which would be liberated in an eruption," she said.
Juan Salazar, the mayor of Penipe, one of 10 villages evacuated last week from the western slopes of Tungurahua, said 3,000 acres of crops and pasture have been damaged by ash from the volcano.
There have been no lava flows since the volcano began spitting out ash in December, he said.
Villagers return by day to tend to their crops and farm animals but stay in temporary shelters outside the danger zone at night.
Salazar said the government has decided to provide new houses for 286 families that cannot return to their homes at night. He said the families would receive the keys to the houses on Feb. 9 along with small plots for growing crops.
Tungurahua erupted in July and August of 2006, causing at least four deaths. The eruptions forced the evacuation of thousands of villagers and damaged thousands of acres of crops buried under tons of ashes and lava flows.
Indonesian mud volcano still active!
It continues to erupt enormous amounts of mud and recently chased over 100 people from their homes.
Chilean volcano eruptions trap over 50 people
"What's most important right now is the rescue of these 53 people," said Carmen Fernandez, the director of Chile's National Emergency Office (Onemi).Their escape was cut off when roads were flooded by a local river that swelled with meltwater following the eruption of the snowy volcano.
The Llaima volcano in southern Chile erupted late on Tuesday, sending a column of smoke and ash into the air and spewing lava down the east side of the mountain.The Conguillio National Park, about 50 miles (82 km) from the city of Temuco, was closed off to visitors on Wednesday and authorities asked curious tourists not to get too close.
"At this moment I would recommend against tourism in the area," Fernandez said on national television.The volcano is one of the country's most active and is in the Araucania region in southern Chile.Before the eruption, people in the towns closest to the volcano said they heard loud noises underground.
The volcano began erupting at 18:20 p.m. (2130 GMT) on Tuesday and it was unclear how long it would continue.The 10,253-foot (3,125-meter) Llaima volcano has frequent moderate eruptions.
Saturday, January 05, 2008
Chilean volcano erupted!
Local television images showed a column of smoke visible from many miles away.
"The Llaima erupted at 18:20 (2120 GMT) but we still don't know if it's a permanent or sporadic eruption. There is lava flowing toward the Argentine side but nothing on the Chilean side. But we are evaluating," a source at the National Emergency Office told Reuters.
The 10,253-foot (3,125-meter) Llaima volcano, one of Chile's most active, has frequent moderate eruptions.
The volcano is in the Araucania region in southern Chile, inside Conguillio National Park and about 50 miles (82 km) from the city of Temuco.