Cum am dovedit cu un dram de noroc vulcanul din Islanda (I)

Two eruptions in a month after volcano is dormant for 200 years

"After lying dormant for more than two centuries, the Eyjafjallajoekull volcano in Iceland has now erupted twice in a month, bringing chaos to northern Europe and destruction to its surroundings. Last night's eruption under a glacier, which spewed massive clouds of ash miles into the sky, was 10 to 20 times more powerful than the one last month, scientists said.

But disruption could last for weeks because the volcano's last eruption lasted two years from 1821 to 1823. Today's caused local rivers to rise by up to ten feet as the ferocious heat melted the glacier, turning it to water which gushed down the mountain.

Iceland's main coastal ring road was closed near the volcano, and workers smashed three holes in the highway to give the rushing water a clear route to the coast and prevent bridges from being swept away. Emergency workers rescued scores of tourists from around the glacier as it spewed smoke and steam.

Forecasters said Londoners will have an astonishing sunset tonight due to the Icelandic eruption. The Met Office said a vivid "volcanic lavender" sunset was likely.

Eruptions create what experts call a "volcanic aerosol" - a colourful mixture of ash and sulphur compounds - in the stratosphere. This scatters an invisible blue glow which, when mixed with the red light of the setting sun, produces a vivid crimson and violet hue.

The eruptions could affect the UK until early next week, and cause changes to temperatures across Europe.

The problem is that we have an area of high pressure, which is pushing the cloud from Iceland directly over Britain", said Brendan Jones of Meteo-Group. "That will not change until early next week, so as long as the volcano keeps erupting, we will have the ash cloud."

At 11am, the ash cloud was at around 20,000 feet and Mr Jones confirmed Britain was unlikely to see much of it because the ash is so diluted. The most noticeable effect is likely to be at sunrise and sunset, when the particles are illuminated.

"The sky isn't going to go dark, and it's unlikely we will see any deposits at all on the ground."

However, Mr Jones said previous eruptions have caused major problems. "If you look back in history there have been some periods where the weather has been changed by big volcanic eruptions like Mount Tambora and Mount St Helens."

In 1815 a huge eruption by Mount Tambora on the Indonesian island of Sumbawa spewed out massive amounts of sulphur dioxide which combined with water vapour to form a sulphuric acid mist that reflected sunlight away from the earth.

That caused such a drop in temperatures that 1816 became known as "the year with no summer". 

Airlines are right to be cautious. This ash could cause engines to shut down 

Volcanoes demand our respect. As the Indian subcontinent headed for its collision with Asia 55 million years ago, the crunch that created the Himalayas triggered intense volcanic activity that some blame for the demise of the dinosaurs.

In today's issue of New Scientist we describe how an eruption of a supervolcano on the Indonesian island of Sumatra 74,000 years ago was the largest on earth in the last two million years and so violent that it shaped human evolution.

Now flights across the UK have been severely disrupted as a result of a plume of volcanic ash drifting into airspace from Iceland. Airlines are right to be cautious. In the past 30 years, about 100 jets have been damaged flying into volcanic ash.

There is the famous example of British Airways Flight 9 from Heathrow to Auckland, which cruised into a cloud of ash thrown up by Mount Galunggung in Indonesia, resulting in the failure of all four of its engines. The captain announced: "Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them under control. I trust you are not in too much distress."

The plane plunged from 36,000 feet to 12,500. It was able to glide far enough to escape the ash cloud and restart the engines, allowing the aircraft to land safely. All four engines had to be replaced.

A few days later, another 747 flew into the ash cloud and suffered engine damage. It performed a successful two-engine landing.

Ash can cause all kinds of damage. When ingested by jet engines, engine performance deteriorates as glass from melting volcanic ash coats components.

Ash is hard, abrasive and mildly corrosive. Any forward-facing surface of an aircraft is likely to be damaged, including the cockpit windows, landing light covers, wing edges, tail rudder, engine cowlings and the nose cone.

A phenomenon similar to St. Elmo's Fire can occur, where blue sparks seem to flow up the outside of the windscreen, or a white glow can shimmer at the leading edges of the wings and engine inlets.

The windows of the cockpit may become so badly scratched that pilots can hardly see the runway.

Some particles will travel through the plane's ventilation ductwork, so there is a smoky or acrid odour. The ash can also clog filters and spread throughout the cabin.

Airlines are well prepared for the plume of ash from Eyjafjallajoekull in Iceland. In July 1991, they met meteorologists and experts to determine what volcano data the aviation industry needed. The month before saw the eruption of Mount Pinatubo in the Philippines, when 20 aircraft flew into ash.

I am sure that many passengers will complain about the cancellations. They will roll their eyes and mutter about today's risk adverse culture. In light of the hazards, the measures taken today are reasonable. The outstanding question is how long the eruptions will last. It could be hours or days, perhaps months or even longer."

(articol preluat din London Evening Standard de joi, 15 aprilie 2010, ziar distribuit gratuit)

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