A volcanic eruption is a potent reminder of the power, and potential devastation, of geological events.
But advances in earth science mean they can now be predicted.
The external behavior of volcanoes, including temperature levels and the release of volcanic ash, is now monitored.
Dr Larry Malinconico, Volcanologist - "As the volcano starts to heat up and magma comes closer to the surface, it's gonna have increased sulfur dioxide, increased HCl, the temperature's gonna go up here, and all over here we're gonna start to see a whole lot more gas come out."
Ground deformation can also occur, where the ground swells as the magma rises.
Mount Etna, Sicily
Geologists studying Europe's largest volcano, Mount Etna, currently use sophisticated GPS receivers to record changes in ground level of several centimeters - which could indicate the onset of an eruption.
But for longer-term prediction, scientists turn to seismology – the study of earthquakes.
Prof Bill McGuire, Seismologist - "Seismology has been studied on volcanoes since the middle part of the 19th century. And it's critical because you don't get a volcanic eruption without seismic activity, without earthquakes."
As magma pushes upwards, a seismometer records the sound of rock breaking.
Seismology - study of vibrations in the Earth
But this method remains inaccurate for predicting the exact time of eruptions.
Seismology can also be used to measure the resonance of the magma.
When a volcano is about to erupt, the magma resonates more frequently - creating a pattern on a seismometer called a long-period event.
Dr Bernard Chouet, US Geological Survey - "The volcano is singing its song, I mean actually this is like chirping if you want, with these sustained waves from the long-period event."
Like a cork in a bottle, as the pressure builds up with each wave, the volcano will eventually blow.
In the year 2000, this method of studying long-period events allowed tens of thousands of people to be evacuated from the vicinity of Mexican volcano Popocatepetl, after scientists successfully predicted its eruption.
4th December 2000
30,000 people saved
It is hoped that these advances in predicting volcanic activity mean future eruptions shouldn't cause casualties.
As before a volcano erupts, there will always be warning signs.