Periodicity

clipped from www.newscientist.com We're not quite back to the pre-plane era, but air travel over and around the north Atlantic might get a lot more disrupted in the coming years. Volcanologists say the fireworks exploding from the Eyjafjallajökull volcano on Iceland, which is responsible for the ash cloud that is grounding all commercial flights across northern Europe, may become a familiar sight. Increased rumblings under Iceland over the past decade suggest that the area is entering a more active phase, with more eruptions and the potential for some very large bangs. "Volcanic activity on Iceland appears to follow a periodicity of around 50 to 80 years. The increase in activity over the past 10 years suggests we might be entering a more active phase with more eruptions," says Thorvaldur Thordarson, an expert on Icelandic volcanoes at the University of Edinburgh, UK. By contrast, the latter half of the 20th century was unusually quiet.