Why volcanic ash breaks planes

Planes in the UK have been grounded due to a massive cloud of volcanic ash drifting across the North Atlantic – but why take such drastic measures?

The cloud currently drifting at altitudes of up to 11km over the UK consists of extremely fine rock, mineral and volcanic glass particles. The cloud formed because molten rock contains dissolved gases that expand and escape from the volcano in a violent explosion that shatters the solid rock into minuscule bits of dust. The finest particles ascend high into the Earth’s atmosphere where they are subsequently dispersed by high-altitude winds.

There are many dangers associated with flying through these particles. First, the ash ‘sandblasts’ the front windscreen of the plane, meaning the pilot must rely entirely upon the vehicle’s instruments. The second, and arguably more deadly consequence of flying a jet aircraft through volcanic ash, is the damage it does to the plane’s engines. Upon entering the engine, the dust particles immediately begin to accumulate, clogging up and fusing on to all parts of the engine. Because the temperature inside a jet engine can reach 2,000ºC, the ash, which contains glass particles, turns into molten glass in the combustion chamber. It then sticks to any moving parts, jamming turbines and blocking vent holes that supply cold air to the cooling systems. At this point the engine simply will not work.


This satellite image of the ash plume over the North Atlantic was captured by NASA’s Moderate-Resolution Imaging Spectroradiometer (MODIS) at 11:35 UTC (7:35 am EDT) on 15 April 2010. Copyright NASA 2010.