Natural events such as volcanic eruptions can test faultlines in society – as well as those in the Earth’s crust from which they arise.
Although Eyjafjallajokull in Iceland is a fairly small volcano, its eruption brought air travel to a standstill – and exposed the priorities of the transport companies.
British Airways seemed more concerned about maintaining its profits than rescuing stranded passengers, while ferry companies saw their chance to cash in by tripling fares.
What causes volcanic eruptions? A major step forward in our understanding of these events came with the discovery that the Earth’s outer crust is not static but consists of moving, overlapping plates.
The vast forces involved as adjacent plates separate, or collide, leads to tensions that can give rise to earthquakes or volcanoes.
Iceland’s volcanic nature is due to it being situated where the north American and European plates are slowly moving apart.
Earthquakes result from adjacent plates literally rubbing each other up the wrong way.
Volcanoes are created when the intense forces generated by plates colliding or pulling apart cause the underlying rock below the crust to liquefy, forming a reservoir of molten rock or magma.
A build up of pressure can lead to magma being forced to the surface in an eruption. But magma reservoirs are often many kilometres below the surface, which makes it difficult to predict the likelihood and force of such explosions.
So far Eyjafjallajokull’s eruption has been a relatively mild affair.
So why has it caused so much chaos? One reason is the fact that the eruption took place under a glacier.
In this situation the magma pushes its way up through ice and consequently cools extremely quickly, shattering into fine particles and also generating steam.
The resulting combination is light enough to be carried far into the sky, right into the flight path of most aeroplanes.
Airline bosses now say the blanket ban on flights was an “overreaction”. But there was a good reason for caution. If volcanic ash particles enter a plane’s jet engines, they can melt and clogs them.
In 1982 a British Airways 747 flew into an ash cloud over Indonesia and all four of its engines failed. It was only prompt action by the pilot, who flew the plane like a glider until the engines eventually re-started, that prevented disaster.
Many were confused by the sudden decision that it was safe to fly again. But the change of heart seems to have less basis in new scientific evidence than lobbying by the airlines.
One source of confusion is that there is currently no definition of a safe concentration of ash for different aircraft. Yet ironically it is the airline industry itself that has resisted previous attempts to set such safe limits, because of fears of legal action should an accident occur.
What about the future? It still remains to be seen whether this eruption is merely the prelude to much bigger explosions. Previous eruptions of Eyjafjallajokull have triggered the eruption of Katla, a nearby volcano that is ten times more powerful.
A more long-term concern is that the ice that currently covers large areas of the planet is beginning to melt due to global warming. This could release tensions in the earth that might increase the frequency and intensity of volcanic activity.
The prediction of eruptions and their effects is fraught with uncertainty.
But scientific understanding and monitoring technology are now so advanced that we ought to be able to anticipate and plan for future emergencies.
Based on our recent experience, however, I would not put too much faith in the ability of our rulers to do so.