When Mount Galunggung in Indonesia erupted in June 1982 a British Airways passenger jet flew into its plume. The engines were choked by the ash and the aircraft fell thousands of feet before the pilot was able to restart them, narrowly avoiding disaster.

There were 17 similar incidents when Mount Pinatubo in the Philippines erupted in 1991, but there is still no system in place to prevent plumes causing crashes. Such tragedies are, according to Peter Francis of the department of earth sciences at the Open University, "accidents waiting to happen".

One solution, he says, would be on-board radar systems which could detect ash so that pilots could navigate round it in the same way they currently do around thunderstorms. The technology exists, but airline companies are unwilling to foot the bill.

Radar is one form of remote sensing (the others use light or infra-red radiation) which Dr Francis thinks has great potential for monitoring volcanoes to save lives: not only the lives of the public at risk from eruptions, but also the lives of scientists studying them. Researchers using remote sensing do not, after all, have to put themselves in danger by approaching their subjects too closely. The point was poignantly made at a Royal Geological Society meeting dedicated to the memory of Open University professor Geoff Brown, killed in 1993 while monitoring a volcano in Colombia.

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Remote sensing and onsite monitoring of volcanoes have become more sophisticated over the past decade, but the meeting underlined the risks still involved. Arrays of sophisticated instruments now produce data crucial to predicting eruptions: changes in temperature and ground movements, seismic activity, gravity shifts due to changes in the plumbing of the volcano, magnetic field changes due to the heating of the magnetic rocks under the surface, and the amount and composition of gases being emitted.

But Dr Francis argues that the data being collected should be interpreted more efficiently and made available more quickly to those responsible for civil defence, particularly when active volcanoes are in densely populated areas.

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Franco Barberi of the department of earth sciences at the University of Pisa described how he and his colleagues anxiously monitored Vesuvius and Campi Flegrei in Italy between 1982 and 1984, when both volcanoes seemed likely to erupt.

With 800,000 people at risk around Vesuvius, and 200,000 around Campi Flegrei, and with the civil defence authorities demanding a month's notice of an eruption so they could evacuate the people, pressure on the scientists was intense. As it happened, they correctly forecast that the volcanoes would not erupt.

The International Decade of Natural Disaster Reduction, now half-way through, has resulted in scientists focussing their efforts on particular volcanoes and setting up more monitoring systems.