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Volcanic eruptions can be predicted by magma chemistry

In 79 AD, Mount Vesuvius erupted and buried the ancient city of Pompeii beneath several tonnes of molten lava and hot ash.

The loss of life and destruction was catastrophic and remains one of the most infamous natural disasters ever seen.

Since then, scientists have been trying to predict when the next super eruption might occur. 

Now, a new study has revealed that by looking at the chemical make-up of the magma, researchers could predict just how explosive a volcano could be.  


Volcanoes have two main types of eruption: effusive and explosive. An effusive reaction consists of a gentle and steady flow of lava on the surface. Explosive reactions are far more violent. Pictured is Mount Etna


The research shows that the type of reaction depends on the chemistry of the magma. 

The presence of certain chemicals alters the viscosity of the magma.

A highly viscous (thick and slow-moving) magma is more likely to explode violently than a fluid magma.

When magma rises to the surface, the water becomes bubbles and this increases the pressure.

In thick and slow moving magma the pressure can not escape and therefore builds up before it blows violently. 

In fast-moving, fluid magma the bubbles can escape and this causes an effusive eruption which is far less violent and dangerous. 

Aluminium, sodium and potassium play a big role in how viscous the magma is. 

Knowing the chemical composition allows for an estimate of how explosive and damaging a volcanic eruption will be.  

Scientists say certain chemicals alter the viscosity of the magma which has a direct impact on it’s explosiveness.   

Dr Di Genova, an expert in experimental volcanology and petrology at the University of Bristol and co-author of the study, said: ‘We have found a tipping point at which magmas fluidise or stiffen.’ 

‘If the viscosity of the magma is very high (think about honey in the fridge), bubbles will not be able to grow easily and they will develop an extremely high (over)pressure.

‘On the other hand, if the magma viscosity decreases, bubbles can grow and escape calmly (like a bottle of sparkling water),’ said Dr. Di Genova.

‘We found that changes in sodium, potassium, aluminium and iron content affect the magma viscosity and govern the eruptive behaviour,’ he continued.

More potassium will result in a more explosive reaction whereas more sodium will likely cause a more gentle eruption.

They also found that an ‘infinitesimal’ change in aluminium content can also dramatically affect the outcome. 

The changes in chemical concentration happens at the nanoparticle level and such fine margins could explain why some volcanoes exhibit both behaviors in a short period of time. 

Previously,it was unknown why the same volcano can sometimes erupt effusively and sometimes explosively. 

‘We have presented evidence to solve this mystery,’ says Di Genova. 

Effusive and explosive reactions are wildly different and have hugely different impacts on human life. 

Whilst volcanic eruptions can not be stopped, knowing how powerful they are going to be would provide invaluable information to minimise the risk to human life.

Bubbling magma: The viscosity of the magma is key to how explosive an eruption will be. Amounts of some chemicals affect this and can be the difference between an effusive and an explosive eruption 

Bubbling magma: The viscosity of the magma is key to how explosive an eruption will be. Amounts of some chemicals affect this and can be the difference between an effusive and an explosive eruption 

Whilst the information from this study provides new insight into how eruptions work and what triggers the most damaging ones, timing volcanic systems and predicting when they will erupt is still extremely difficult. 

In future research, the scientists hope to focus on understanding how far a volcanic system is from such a tipping point.

Di Genova said: ‘We need to develop new infrastructure to mimic magma physical conditions in the laboratory. 

‘This means that we need to work at very high pressure (2 thousands times ambient pressure) and high temperature (up to 1400 degrees Celsius).’

This study allows scientists to know what to look for and the warning signs, looking at how that can be applied practically to an erupting volcano is the next step.