Bali, where more than 180,000 people have been evacuated from the area around Mount Agung volcano, has been shaken by a 6.7 magnitude earthquake after experiencing a decrease in seismic activity over the weekend.
The earthquake, reported about 450km away from Bali's volcano, caused huge spikes in the seismogram.
Mark Spychala, atmospheric scientist at St Edward's University in Texas, tweeted "Some serious readouts on the seismogram in the last hour from #Bali #volcano Mt. #Agung and nearby sites. Unsure about status."
Source: Mark G. Spychala
Source: Mark G. Spychala
The United States Geological Survey (USGS) said that there was no threat of a tsunami, but fatalities and economic loss had been raised to green. USGS says: "Green alert for shaking-related fatalities and economic losses. There is a low likelihood of casualties and damage."
It has been over a month since the Bali volcano, Mount Agung, was declared as being in critical stage. Thousands of tremors were being recorded per day, but since October 22, that dropped to about 200 tremors per day which had surprised scientists.
Since the warning was issued on September 22, 180,000 people living within the 12km exclusion zone have been evacuated to safety zones where food, blankets and water is being provided.
Bali officials said that tourists should not cancel their holidays but should be aware that if an eruption was to happen, airports and flights would be affected and possibly delayed and people diverted to other unaffected airports nearby.
Every year millions of tourists come to Bali from across the world, mainly from Australia, China and Japan.
The last time Mount Agung erupted was in 1963 killing 1,300 people and lava flowed as far as 7km from its crater. Sulphur-based particles which emanated from the eruption created a shield which reduced solar radiation and caused the global temperature in that year to drop by between 0.1-0.4C.
Other dangerous volcanoes with imminent eruption
A supervolcano is a volcano which has the ability to erupt and spew out a minimum of 1000km3 magma. A normal volcano releases about only 1km3 of lava.
It is not only Bali's Mount Agung which is in critical stage, but also Italy's supervolcano, Campi Flegre, near Naples. It sits right beneath the ancient town of Pozzuoli. Campi Flegre, which translates to 'burning fields', last erupted in 1538 but it was small eruption in comparison to the volume of magma estimated to be beneath the surface. The last time it showed signs of seismic activity was in 1983 but it has been dormant ever since.
The supervolcano, which is a caldera (a large volcanic crater with a collapsed volcano mouth due to an eruption), has 24 craters. It is unsure where it will erupt, when it does, as blockages in the magma's path has caused it to migrate. The eruption may take place closer to Naples where 3-million people currently reside or beneath the ocean.
Its last large eruption happened 39,000 years ago, and is the largest volcano eruption in the past 200,000 years in Europe. The eruption saw lava and rocks being shot kilometres into the air and hundreds of kilometres across Europe.