'Dormant' volcanoes found to be active

Scientists say they have been shocked to discover that four dormant volcanoes in South America are in fact active.

Researchers used satellite imaging techniques to look at movements in the ground, and they say their results have implications for volcanic areas around the world.

" For most of the world's volcanoes, we have no idea of their level of activity "
Professor Mark Simons

Nine hundred volcanoes in the Andes mountains in Chile were scrutinised.

Satellites took pictures of the same landscape at different intervals and researchers compared them.

Any geological changes between the pictures were shown as what is called a radar interference fringe.

This looks rather like the patterns made by a drop of oil in a puddle, and tells scientists that the ground is moving.

'Census needed'

Professor Mark Simons of the California Institute of Technology said what his team saw was quite alarming.

"This suggests that, for most of the world's volcanoes, we have no idea of their level of activity," he said.

"[It] really promotes the idea that we need to start developing a census of the world's volcanoes to look at the level of their activity."

It is possible that many more supposedly dormant volcanoes could be active.

But although scientists can tell when the ground is deforming underneath a volcano, it does not necessarily mean it will erupt.

If there is an eruption, however, or even an earthquake, researchers hope the same satellite technology could one day be used to locate the worst affected areas more quickly, enabling emergency services to get help to those most in need.