Last month, a volcano erupted In 1,03,000 square kilometre Island nation named Iceland, situated on the fringe of the Arctic Circle, spattering most of the European sky with its volcanic ash. This small country (population: 3,00,000) has nearly 200 volcanoes so It Is no wonder that one or the other is always active. Moreover, 80% land of this country remains perennially ice covered. Both these geographical features have earned for it the nickname ‘Land of hoe and Ice’. However the latest eruption of the volcano having tongue-twister name, ‘Eyjafjallajoekull’, has given rise to an unusual side-effect which is worth knowing in some detail.
Why there are so many volcanoes in Iceland?
Although Iceland is not much more than half the size of Gujarat, how come there are 200 volcanoes? Geological structure of the Earth is responsible for it. Iceland is situated on the mid-oceanic ridge of the Atlantic Ocean (refer accompanying map) where two major tectonic plates of the Earth’s crust-the North American Plate in the west and the Eurasian Plate in the east-converge. Collisions of both these tectonic plates moving towards each other over the eons created many faults through which lava has been erupting and cooling into igneous rock; and creating conical shaped volcanoes. Iceland and its volcanoes have been formed by such volcanic activity that is still going on.
Clouds of ash: Form quickly but disperse slowly
Clouds of ash spewed by Iceland’s volcano reached the upper layer of atmosphere known as stratosphere after penetrating through troposphere, the middle layer; and started drifting eastward in the prevailing direction of the wind.(See picture on the side). Within a short span of four days these clouds had covered the sky above 24 European countries fully or partially. The cloud of ash could spread quickly because the wind blows at the velocity of 100-150 kilometres per hour in the upper reaches of the atmosphere.
How long will it take before the volcanic ash starts settling down on the ground? Observations by the scientists have shown that the specks of ash having diameter of 0.005 kilometres remain suspended in the troposphere for about ten weeks whereas more tiny specks of 0.001 kilometre diameter remain suspended in the atmosphere up to two years. It should be noted that these observations pertain to windless condition. In windy conditions the particles will most probably remain suspended in the atmosphere for a much longer period.
How volcanic ash affects the civil aviation?
The ash spewed by Iceland’s volcano has brought civil aviation to a standstill in Europe. Volcanic ash can imperil the safety of a passenger airliner in more than one way. For example,
- Turbofan engines of the modern jet airliners have massive fans in the
front to suck in and compress copious amounts of air for the combustion of fuel. Tiny particles of ash suspended in the air constantly colliding with the blades of turbofans at the velocity of nearly 900 kilometres per hour can damage the blades with their abrasive action.
- There is a tube known as ‘pilot tube’ near the plane’s nose for measuring its speed. Any blockade ¡n this tube due to accumulation of ash can mislead the pilot about the plane’s actual speed. Excessive reduction of speed by the pilot due to incorrect speed indication can cause the plane to lose the necessary force of lift and bring it plummeting down.
- Volcanic ash contains tiny particles of silica. If these particles melt again (they were in molten form when spewed by the volcano) in the combustion chamber of the plane’s engine they can jeopardise its working to very dangerous extent. If semi-solid silica blocks the fuel nozzle from which the fuel is injected into the combustion chamber, the engine would stop mid-air.
- Innumerable dents made by billions of tiny particles of ash striking against the wind screen per second can make it practically opaque within a short time preventing the pilot to see clearly. This problem can expose the plane to serious risk.
Will the cloud of ash affect the climate?
The canopy of ash cloud spread in the atmosphere by Iceland’s volcano is going to reflect much of the sunlight back into the space in the days and months to come. However, it will not obstruct the heat waves escaping into the space from the Earth. This phenomenon is bound to lower the average temperature of Europe if not the entire world’s. For example, when a volcano named El Chichon had erupted in Mexico in 1982, average temperature of the tropics had reduced by 2° Celsius. Therefore, the possibility of a harsh winter in Europe next year can not be ruled out.