Andrew DEREK UK
DIS Legend
- Joined
- Mar 8, 2004
- Messages
- 29,143
Wait a minute. What do you mean "the bigger one next to it"????? What's that? And how serious is that risk?
Breaking news!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
My Sister is stuck in Spain!!!!, can anyone who thinks they can get her home, tell us how?????????
From the BBC again.
Angry sisters
Eyjafjallajoekull, which is currently filling the sky above northern Europe with ash, is a minor player in Icelandic terms - though its last eruption lasted for more than a year, from December 1821 to January 1823.
The most ominous thing about Eyjafjallajoekull is that its eruptions have historically preceded eruptions by one of Iceland's most feared volcanoes, Katla.
Fortunately, Katla, one of the two so-called Angry Sisters, has shown no sign of unusual activity in 2010
Katla is located under the vast Myrdalsjoekull glacier. One of the highest volcanoes in Europe at 1,512m (4,961 ft), its crater has a diameter of 10km. Any eruption would raise fears of major flooding due to the melting of the glacier.
Its last major eruption occurred in 1918, with a smaller eruption in the 1950s. Historically, it tends to erupt every 40-80 years.
The second of the Angry Sisters is 1,490m Mount Hekla, Iceland's most active volcano.
In the Middle Ages it was believed to be one of the gateways to hell, or Judas's prison. An eruption in 2000 spewed columns of ash several kilometres into the sky, and caused a lava flow 7km long.
In 1973, there was an eruption near the nation's premier fishing port, Vestmannaeyjar, on the southern island of Heimaey. A mile-long fissure rapidly opened, bisecting the island. Spectacular lava fountains followed.
The lava flow continued for five months and around 400 homes close to the rift were destroyed by ash-fall, or consumed by lava flow.
But within hours of the eruption, nearly all of Heimaey's 5,300 residents were evacuated to the mainland by the island's fishing fleet.
The picture of whether Iceland's volcanic eruption is intensifying or abating remains murky, particularly since the webcam images on Friday were shrouded in cloud.
Scientists are struggling to work out if the eruption itself could continue for days, weeks or even months.
But, as Professor Jon Davidson - an earth scientist from the University of Durham - told BBC News, it was not the eruption per se that caused the problem.
"It's the fact that the prevailing winds are driving the ash plume over the UK," he explained.
And scientists in Iceland reported on Friday morning that the volcano was continuing to generate a tall plume of ash - contributing to the cloud already drifting high in the atmosphere over the UK.
So the cloud that has grounded UK flights appears to be continuing to grow. And the researchers say that could go on for several days.
Dr David Rothery, a volcanologist from the UK's Open University agrees this could happen, but suggests that it is unlikely.
Intense and explosive
"It is usual that an explosive eruption like this has its most intensive point at the start and that it gradually subsides," he told BBC News.
What scientists are trying to find out, he explained, is if the [ongoing] eruption is explosive enough to create a tall column of ash and continue feeding the plume.
It is the explosion that initially forces the ash upward - expanding gas at the eruption site generates thrust. From there, the cloud of dust and gas rises because it is warmer than the surrounding air.
So if the eruption continues to be intense and explosive, giving the ash that initial upward thrust, the plume that has been blown in UK and European airspace could continue to grow.
But according to the most recent reports from the UK Met Office and the Icelandic Met Service, ash is now being released in pulses rather than a continuous plume.
Unpredictable eruption
Professor Davidson said that there was no way to reliably predict how the Eyjafjallajokull volcano will behave.
"This eruption started on 20 March," he said. "So in a sense it's been erupting already for almost a month.
"We will be watching the seismic activity because [from that] we will be able to see the predictions in changes in the behaviour of the volcano that will herald a increase or decrease in its activity."
And currently, there appears to be far less seismic activity in Iceland than in the days running up to Wednesday's eruption. This could mean that the worst is over.
But researchers in Iceland, who have analysed the first sample of ash produced by the volcano, have found that its composition could contribute to the explosiveness of future eruptions.
"The magma is much richer in silicon than the basalt that was previously erupting in the initial stages," explained Dr Mike Burton, senior volcanologist at the Italian National Institute for Geophysics and Volcanology.
"This has two important implications. Firstly, the ash produced will be finer, with smaller particles compared with basalt."
Finer ash will rise more easily.
Secondly, he said, "the activity may well be more explosive because of the higher viscosity of the magma."
The more viscous the magma, the less easily gas flows through it. "Therefore it's easier for pressure build up to occur, leading to more violent explosions."
Through Thursday and Friday, the volcano has continued to feed an existing large plume of ash that is moving very slowly eastward at a height of about 30,000ft.
Aviation authorities cannot risk reinstating flights when this plume is within airspace, as the ash could clog jet engines and cause them to fail.
Jim Haywood, a researcher from the Met Office confirmed on Friday that he and his colleagues had detected the plume above the UK.
"It's patchy but it's certainly there, although you won't see it with the naked eye," he said.
"We are formulating some forecasts about how long this may last, but that will be very dependent on the eruption from the volcano, so we're working closely with scientists in Iceland to get the most up to date information about the eruption height and intensity."
I bet some UK/Euro companies were wishing they had a few of these right now!
A drigble wouldn't likely be effect like a jet is.
