The Arenal Volcano in Costa Rica erupted unexpectedly in 1968, destroying the small town of Tabacón. Since October 2010, Arenal has become dormant, with no explosions since December 2010

Initial damage in areas near the volcanoes 

In the 1997 drama, Dante's Peak, Pierce Brosnan arrives in a town only to discover that the long dormant volcano may wake up at any moment

Firstly, the people in the firing line of the eruption would be affected, not only by the flow of magma from the volcano, but also from the huge ash clouds expelled.

Pyroclastic flows are fast-moving clouds of rock, ash and gas that are very hot, with temperatures rising up to 1000°C.

These would be impossible to outrun or even drive, as they can travel up to 450 miles per hour.

As well as affecting people near the volcano itself, pyroclastic flows can cause destruction for up to 100 miles from the site.

The number of people living near volcanoes that this would affect is massive.

For example, around three million people live near Mount Vesuvius, while 130 million people live on the island of Java which alone has 45 active volcanoes.