UK and Russian scientists say they are a step closer to predicting how dangerous a volcano is after developing a method that lets them figure out how individual volcanoes are 'plumbed'.

The new approach means researchers need only analyse a single chunk of rock from a volcano to work out how big and deep its magma chamber is.

The same method also lets them calculate the length and width of the vent that brings the magma from the chamber to the surface.

Having both measurements is vital for predicting how hazardous a volcano will be.

'Generally speaking if a volcano has a big magma chamber and a narrow, short vent, the volcano tends to be more explosive than a volcano with a small chamber and wide vent,' says Professor Jon Blundy from the University of Bristol, a member of the research team.

'So, if we know the details of the plumbing system underneath a volcano, we're in a better position to say how dangerous it is likely to be,' he adds.