The Current

'Extremely dangerous': Unclouding the threat of Bali's Mount Agung volcano

What happens when a volcano explodes? What would be the outcome? Volcanologist Glyn Williams-Jones explains.
Indonesians carry their belongings during an evacuation, on Nov. 26, 2017. (Firdia Lisnawati/Associated Press)

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As many as 100,000 Indonesians are on the move.

They've been ordered to leave their homes near an active volcano on the tourist island of Bali after Indonesia raised its volcano alert to its highest level on November 27, 2017.

Mount Agung is spewing grey ash 30 thousand feet into the air. Volcanic debris and water are flowing down the volcano's slopes.

Tens of thousands of international travellers — including at least 400 Canadians — are stranded on the island after Bali's international airport was shut down by the dangers of ash.

The fear is that an even larger eruption may be imminent.   

Glyn Williams-Jones, a professor of Volcanology at Simon Fraser University, says such an event could have devastating consequences.

"It can be extremely destructive and it really depends on how close you are," Williams-Jones tells The Current.

"We can have lava flows coming down; bulldozers of molten rock. Here in Bali, Indonesia, one of the bigger problems are these mud flows … these are incredibly erosive down the river-valleys and really just destroy everything in their path."

Williams-Jones says the most dangerous outcome are clouds of ash and gas descending down the flanks of the volcano, known as "pyroclastic flows."  

"These percussive flows can travel hundreds of kilometers an hour and are many hundreds of degrees Celsius in temperature — so extremely dangerous."

A farmer walks with his cattle as Mount Agung volcano erupts in the background in Karangasem, Bali, Indonesia Nov. 28, 2017. (Johannes P. Christo/Reuters)

The last time Mount Agung erupted, in 1964, it took the lives of an estimated 1500 people.

But despite warning signs Agung will go off again, there's a possibility it will recede.

"You know volcanoes are tricky beasts to understand. And it's not the first time that a volcano has gone into a situation like this, a level of activity, and then for one reason or another we don't really understand — it calms back down again," says Williams-Jones.

"However given the signs of activity that we're seeing now, really the only thing you can do is prepare for the worst and and hope for the best."

Listen to the full conversation at the top of this post.

This segment was produced by The Current's John Chipman and Susana Ferreira.