Fear surrounding the eruption of Mount Agung in Bali escalated after nearby Mount Sinabung, in Northern Sumatra, suddenly exploded on Wednesday.
Shocking Twitter footage shows the volcano spewing ash 2.5km into the air.
Thick smoke then surrounds the volcano, expanding outwards because of the wind.
Thousands of locals were forced to flee from the area and warned to stay at least 7km away in case of further eruptions.
The sudden explosion sparked additional fears over a possible eruption of Mount Agung in Bali which has been under close monitoring for days.
There have been more than 650 instances of seismic activity recorded each day since last Thursday, September 21. On some days there have been almost 1,000 tremors.
The number of people forced to flee their homes near Mount Agung has now topped 144,000, according to Indonesia’s National Disaster Management Authority (BNPB).
A statement from Pak Kasbani, head of Indonesia’s geological agency, said volcanic earthquakes continue to be felt in high numbers with increased magnitude, “indicating brittle failure inside the volcano caused by magma movement."
White steam clouds have been observed rising between 50m and 200m above the summit.
Bali authorities have claimed that tourism has not been affected by the possibility of a volcanic eruption and have urged holidaymakers to still come to the island.
The island’s tourism chief AA Gede Yuniartha Putra said: "Bali tourism is safe. Do not spread the misleading news that Bali is not safe because Mount Agung is on the highest alert status. Please, come and visit Bali.”
But the Australian and UK Government have advised residents of Bali and travellers that ash clouds from the erupting volcano could significantly impact the island.
One of Bali's most active volcanoes forced the island to trigger the highest alert after Mount Agung volcano shows signs of an imminent eruption. The Red Cross reported that 50,000 people have been evacuated from their homes around Mount Agung.
In the last few days, Mount Agung has triggered hundreds of tremors detected by seismographs. Tremor swarms coming from a volcano often preempt an eruption as magma rises to the surface and creates conduits for flow.
There is currently a 7.5-mile exclusion zone around the Bali volcano that is on the country's highest alert and residents have been evacuated. The volcano has not significantly impacted the tourism industry in Bali as Mount Agung is located in the northeast corner of Bali and the tourism center is primarily to the south of the island.
This graph shows why vulcanologists think Bali's Mt Agung will explode soon - look at spike in red trend line showing energy of tremors. pic.twitter.com/4Fb4oMpUIx— Adam Harvey (@adharves) September 24, 2017
In the tweet above, the seismograph shows a sudden and dramatic spike in seismic activity around September 23rd to 24th. In addition, the seismic tremors appear to be increasing in energy, adding to fears that Mount Agung will erupt in the near future.
Latest reports indicate that 50,000 people have been evacuated from their homes to live in makeshift shelters, schools, and town halls. Nearby tourist destinations of Kuta and Seminyak are unaffected at this point and all flights have been operating as normal.
Bali's stratovolcano Mount Agung last erupted in 1963, killing over 1,000 people and damaging infrastructure. During Agung's 1963 eruption pyroclastic debris was ejected 8 to 10 km into the air and lava flowed as far as 7 km from the volcano.
The Bali volcano and Bali itself are part of the Indonesian archipelago, a string of islands created by the subduction of the Indo-Australian plate underneath the Eurasian plate. This subduction both plowed sediment up high enough to form islands but also created volcanism. This volcanism has covered practically the entire island of Bali with lava flows. Some being as old as 1 million years old, others are decades old.
Indonesia and Bali lie in the Pacific "Ring of Fire" which outlines most of the Pacific Ocean's boundaries. The name is a result of the overwhelming volcanic and earthquake activity along the margins of the Pacific. This is due to subduction of the Pacific plate underneath continental plates. Hence, the same mechanism that produces volcanism in North and South America also produce volcanism in eastern Asia.