Aisling Irwin and Juliet Vickery report from the British Association for the Advancement of Science in Birmingham.

A volcanic eruption powerful enough to trigger another ice age is long overdue, a vulcanologist said this week. There are usually two such eruptions every 100,000 years - yet there have been none for the last 70,000 years, said Bill McGuire, head of the centre for volcanic research at Cheltenham and Gloucester College of ³ÉÈËVRÊÓƵ.

Meanwhile a lesser volcano which could nevertheless wreak havoc on both sides of the Atlantic may soon erupt in the holiday isles of the Canaries, he warned.

The volcano of ice-age triggering potential, registering eight (the maximum) on the Volcano Explosivity Index - would do its biggest damage by throwing out debris into the atmosphere that blotted out the sun.

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Such an eruption is likely to happen, almost by definition, where people are least expecting it, Professor McGuire told the British Association. This is because the longer a volcano remains dormant the more violent it is likely to be when it erupts. However, it is most likely to erupt on the west coast of north or south America or in southeast Asia, he said.

In the shorter term, Professor McGuire highlighted the dangers of a volcano at Las Palmas in the Canary Islands. It erupted in 1949, sending a great chunk of the island sliding towards, but not quite into, the sea. Another eruption in the same place could send it crashing into the sea, setting up a great tidal wave that would hit Florida, with waves, possibly tens of metres high, on the other side of the Atlantic.

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He has set up monitoring systems in the Canaries, which could give a few days warning. A tidal wave would take a few hours to cross the Atlantic and he called for emergency procedures to be organised in Florida.