Despite Bali’s Mount Agung volcano spewing huge plumes of volcanic ash, and lava, experts warn complacency is the island’s biggest enemy and that the worst is yet to come, including blinding ashfall and flying rocks that spew out of the volcano.
“This is an eruption, this is 100 per cent an eruption,” volcanologist Dr Janine Krippner told news.com.au.
“Lava is coming out of the volcano, there’s definitely enough to cause trouble. This can get much worse, you can’t outrun this.”
For months, magma inside Bali’s giant, belching volcano has been gradually rising to the top of the volcano, forcing the gigantic structure to rumble and shake.
In August, the volcano slowly began to rumble back to life, and through September the number of tremors recorded at Mount Agung reached about a thousand a day.
Agung’s last eruptions in 1963 produced deadly clouds of searing hot ash, gases and rock fragments that travelled down its slopes at great speed. About 1100 people died in total. There are serious fears the same will happen again.
Lava spread for several kilometres and people were also killed by lahars — rivers of water and volcanic debris also described as cold lava. But the pyroclastic flows are also ones to watch.
“If those come, they can travel 10km within three minutes,” Dr Krippner said.
“You can’t outrun these.”
In Mount Agung’s case, molten rock, which has been accumulating for the past 50 years, has heated up and slowly — thanks to the overwhelming pressure — pushed through the volcanic rock above, finding weaker points to penetrate.
But Dr Krippner said what has changed in recent weeks is that the molten rock has nothing left to push through – it’s reached the top. Now that the lid has quite literally been blown off, the future is an uncertain one.
“The danger is that this is now an open system. Before, it was a closed system which means that there was no easy open access between the magma and the surface,” she explained.
“Now that that has completely made its way through, this can change quickly. It doesn’t have to force its way through the rock any more, now it’s just coming out.”
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Increased temperature in the groundwater created steam filled with gases like sulphur dioxide; it’s been steaming away quite strongly over the last months. Dangerous volcanic gases also fill the air. It’s getting thicker, pulsating.
As it’s doing that, the mountain is shaking as rocks interact with water and ocean sediment, melting, bubbling their way up to their source.
“It’s like shaking up a bottle of Coke and then taking the lid off,” Dr Krippner said.
“It’s the same process before you open a bottle of Coke; there’s gas in it, but you can’t see it because it’s pressurised when they bottle it in the factory. But if you shake that up you’ve agitated the gases and then as soon as you relieve that pressure the gases are coming out so quickly that it’s blowing the Coke into tiny fragments.
“That’s exactly what is happening with Agung. The pressure is being released quickly as it comes out because its coming from below the surface of the earth so there’s a lot of rock and gravity. As it’s being released the gases are coming out very quickly and expanding and just blowing the rock apart as fragments of ash and glass and crystals.”