Eyjafjallajokull , until now barely known, is in the thick of news. The volcanic eruptions in March and April caused air travel to be suspended indefinitely. But why should this happen?

The Prime Minister Manmohan Singh's Air India One from Brazil had to take a flight detour via Johannesburg instead of Frankfurt, to come home to India, as all airports in Europe were closed.

The reason? A volcano below the Eyjafjallajokull glacier in Iceland, 120 km south east from the capital Reykjavik had erupted, spewing thick, dark brown, ash cloud. This cloud spread, drifting across the Northern European skies, shutting down airports across the area. Even Poland and Czechoslovakia had to declare a shut down and join the rest of Europe in closing their airports. So passengers were stranded in airports all over the world.

You might wonder what volcanic ash has to do with airplanes.

What's in the ash?

Scientists conducted an investigation, in the 1980s. They studied the composition of the ash thrown out by any volcano. They found that the dust contained fine particles of glass, pulverized rock and silicates. Put these all together and one gets a composition resembling tough sandpaper, which is normally used to scrape off paint and a lot of tough surface materials.

Pilots are accustomed to flying ‘planes in extremely bad weather and can handle poor visibility. But with volcanic ash this is not the only problem. The ash can destroy the most important parts of the ‘plane's engines, when it collides at high speeds, and can have a destructive effect blowing away surfaces inside the engine. These particles can fuse together when entering the engine where there is extremely high heat, causing damage to the electronics and causing the engine to cease.

Volcanic eruptions are also accompanied by clouds of hydrochloric acid and sulphuric gas.

Professor Janos Bogardi of the University of Bonn, Germany, explains the phenomenon, “The suddenly active volcano in Iceland catapults a tremendous amount of steam and dust into the high atmosphere (around 8000 m height). This plume is propagated by the wind towards Western and Central Europe. Given the tiny size of most of these particles and the wind force, they remain in the atmosphere for quite some time and affect the engines of the ‘planes flying through them.”

(The writer is a fellow with UNEP and UNFCCC)

Mid-air miracle

Captain Eric Moody, the captain of a British Airways Jumbo Jet which was enroute from Kuala Lampur to Perth suddenly found that all four of his engines had failed. There were 247 passengers on board that flight. Captain Moody bravely glided the ‘plane down 20,000 feet without mishap, and managed to restart one engine at 13,000 feet and two others later. After a thorough investigation, it was concluded that the ‘plane which had flown into volcanic ash from Mount Galunggung in West Java, in Indonesia, had suffered extensive damage to its engines due to the abrasiveness of the volcanic ash. This incident initiated new flight procedures and international aviation contingency rules, brought into force by the UN's Civil Aviation Organisation, with particular reference to flying into volcanic ash.

Island mountain glacier

Eyjafjallajökull (translated as island-mountain glacier) is one of the smaller glaciers of Iceland. The icecap of the glacier covers a volcano with a summit elevation of 1,666 metres (5,466 ft). The glacier covers an area of about 100 square kilometres. The volcano, which has a crater three to four kilometres in diameter, erupted in 920, 1612 and again from 1821 to 1823 when it caused a glacial lake outburst flood. It has erupted twice in 2010 — on March 20 and April 14.

Eruptions

A study by the Icelandic Meteorological Office published in December 2009 indicated an increase in seismic activity around the Eyjafjallajökull area during the years 2006–2009. At the end of December 2009, seismic activity began around the Eyjafjallajökull volcano area, with thousands of small earthquakes , seven to 10 kilometres beneath the volcano. The seismic activity continued to increase and from March 3 to 5, and close to 3,000 earthquakes were measured at the epicentre in the volcano. Most were too small (magnitude 2) to be read as presaging an eruption.

On April 14, Eyjafjallajökull resumed erupting after a brief pause, this time in the centre of the glacier, causing meltwater floods to rush down nearby rivers in two flows on either side of the volcano, and requiring 800 people to be evacuated.

Unlike the earlier eruption, the second eruption occurred beneath glacial ice. Cold water from melted ice chills the lava quickly and fragments it into glass, creating small glass particles that get carried into the eruption plume. This, together with the magnitude of the eruption, created a glass-rich plume in the upper atmosphere, which is hazardous to aircraft.