Nearly 100,000 people have been evacuated from the the 7.5 mile danger zone that surrounds the Mount Agung amid fears the volcano could erupt at any time.
The volcano alert in Bali was raised to level 4 – the high possible level which warns that an eruption is imminent.
A thin line of white smoke is rising from the summit and the Indonesia’s National Disaster Mitigation Agency say that it has detected more than 800 tremors so far Wednesday.
Agency spokesman Sutopo Purwo Nugroho said: “The chance that an eruption will happen is quite big. But it cannot be predicted when it will happen.”
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What happens if Mount Agung erupts?
Mount Agung has not erupted in over half a century, when two major eruptions killed about 1,100 people and injured nearly 300 more.
Veterans of the 1963 catastrophe are among the evacuees who have been forced to flee their homes this time around.
Nyoman Smah, who was 16 at the time of the first eruption, recalled a “rain of ashes” falling from the sky.
Speaking to ABC News, she said: “I wore a hat, but it was too big and heavy because of the ashes, so took it off. Those rocks and ashes fell to the eastern river and started flowing down.”
In February 1963, white smoke started billowing from the volcano. Less than a week later, streams of lava began pouring out of the crater and down the sides of the volcano. The molten rock went on to flow up to 4.5 miles.
However, it was the subsequent pyroclastic flows that caused the most devastating loss of life.
A deadly cocktail of scolding hot gas, rocks and ash barrelled off the volcano at hundreds of kilometres an hours, decimating anything and everything in its path.
Indonesian officials are much better prepared for an eruption this year, so the death toll is expected to be much lower if Agung does explode.
Professor Mike Burton, chair in volcanology at Manchester University, believes modern monitoring and communication technologies will allow more locals to get out of danger in time.
In a Q&A on the university’s website, he said: “Planning for a scenario similar to the 1963 eruption with pyroclastic flow run out up to 12 km from the summit is prudent, with a good probability that the actual eruption will be smaller than that.”
Aeroplanes can be badly affected in the aftermath of a volcanic explosion, due to the huge amount of ash that gets pumped into the air.
This ash can build up in a plane’s engine, eventually blocking it entirely.
Tens of thousands of flights were cancelled in Europe in 2010, when Iceland’s Eyjafjallajökull volcano coughed huge clouds of ash into the atmosphere.
The latest Foreign Office advice to Britons planning to visit the region says that “an eruption is possible in the next 24 hours”.
The Foreign Office says: “You should follow the advice of the local authorities and stay outside the exclusion zone which extends between 9 and 12 kms from the crater.
“If there is an eruption, volcanic ash clouds could cause flight disruptions.
“In the event of volcanic ash clouds you should confirm your travel arrangements directly with your airline or travel agent before travelling to the airport.”