Authorities in Indonesia have issued a tsunami alert after a volcano erupted five times in the province of North Sulawesi, spewing a column of smoke more than a mile into the sky and forcing the evacuation of thousands of people from their homes.
Mount Ruang, a stratovolcano, first erupted at 9.45pm local time on Tuesday and then four times on Wednesday, Indonesia’s volcanology agency said.
Officials worry that part of the volcano could collapse into the sea and cause a tsunami, as happened in 1871. Tagulandang island to the volcano’s north-east is again at risk.
The alert level for the volcano, which has a peak of 725 metres above sea level, was raised on Wednesday evening from three to four, the highest level in the four-tiered system.
“Based on the result of visual and instrumental observation that showed an increase in volcanic activity, Mount Ruang’s level was raised from level three to level four,” Hendra Gunawan, the head of Indonesia’s volcanology agency, said in a statement.
Authorities said they were rushing to evacuate 11,000 residents from nearby areas, including the remote island of Tagulandang, home to around 20,000 people.
Some residents were already trying to flee in a panic, according to officials.
“Last night people evacuated on their own but without direction due to the volcano’s eruption and materials in the form of small rocks that fell, so the people scattered to find evacuation routes,” Jandry Paendong, an official from the local search and rescue agency, said in a statement.
He said 20 staff were helping evacuate residents along the coastline near the volcano on rubber boats but called for more boats and equipment so his team could continue.
Authorities widened a 4km exclusion zone around the crater to 6km on Wednesday evening, warning tourists and residents to remain outside of it.
The volcano was still billowing a column of smoke on Thursday morning, prompting authorities to shut the nearest international airport in Manado city on Sulawesi island for 24 hours.
Runways were shut “due to the spread of volcanic ash which could endanger flight safety”, Ambar Suryoko, head of the Manado region airport authority office, said in a statement.
The airport hosts airlines that fly to Singapore and cities in South Korea and China.
There have been no reports of deaths or injuries so far, but more than 800 people were evacuated from two Ruang Island villages to nearby Tagulandang Island, located more than 60 miles north of the provincial capital, Manado, the state agency Antara reported.
Indonesia’s national disaster mitigation agency said residents would be relocated to Manado, the nearest city, on Sulawesi island, a journey of six hours by boat.
In 2018 the eruption of Indonesia’s Anak Krakatau volcano caused a tsunami along the coasts of Sumatra and Java after parts of the mountain fell into the ocean, killing 430 people.
In a statement, Gunawan told people to “be on alert for the potential ejection of rocks, hot cloud discharges and tsunami caused by the collapse of the volcano’s body into the sea”.
Ruang’s initial eruption on Tuesday evening pushed a column of ash 1.2 miles into the sky, with the second eruption pushing it to 1.5 miles, Muhammad Wafid, the head of the geological agency, said in a statement.
The volcanology agency said on Tuesday that volcanic activity had increased at Ruang after two earthquakes in recent weeks.
Indonesia, a vast country of archipelagos, sees frequent seismic and volcanic activity due to its position on the Pacific’s Ring of Fire, an arc where tectonic plates collide, which stretches from Japan through south-east Asia and across the Pacific basin.
