Indonesia: Authorities lower alert status for Ruang Volcano in North Sulawesi Province due to decreasing volcanic activity as of April 22 /update 4

Authorities at Indonesia's Center for Volcanology and Geological Disaster Mitigation (PVMBG) have lowered the volcano alert status for Mount Ruang volcano in North Sulawesi Province from level 4 to 3 (on a four-tier scale) as of April 22 due to a decrease in volcanic activity following days of eruptive activity. Explosive eruptions at Mount Ruang since April 16 have led to evacuations and flight disruptions, not only in North Sulawesi Province but also in parts of eastern Malaysia. The volcano has erupted more than ten times since April 16, emitting ash clouds at least 2.5 km (1.5 miles) above the crater and lava flowing down its flanks; a magnitude-5.3 earthquake near North Maluku Province at 00:40 April 14 could have triggered the volcanic activity. The eruptions produced a volcanic ash plume that spread volcanic ash to nearby roads and villages, as well as disrupting air travel in the region.

Over 11,000 residents of Ruang and southwest Tagulandang islands have been evacuated in recent days due to the threat of ashfall, pyroclastic flows, other volcanic material, and seismically triggered landslides around the volcano. Around 500 homes and other buildings in affected areas have suffered varying degrees of damage caused by the eruptions. As of April 22, authorities have reduced the exclusion zone around the volcano from 6 km (4 miles) to 4 km (2.5 miles) due to the decreasing activity. It has not been confirmed how many of those evacuated will be able to return home; small-scale eruptions distributing volcanic material, including ash and gas, are still possible in the coming days. The PVMBG has also lifted a warning previously issued for a possible tsunami due to the decrease in volcanic activity; there had been fears that parts of the volcano could collapse into the sea.

Sam Ratulangi International Airport (MDC) in Manado, North Sulawesi Province, resumed operations on April 22 after being closed since April 18 due to volcanic ash detected at the airport. Around 150 flights and 19,000 passengers have been affected by the airport closure. In Malaysia, AirAsia (AK) and Malaysia Airlines (MH) canceled several flights to and from airports in the east of the country due to the threat of volcanic ash April 18-19, including Tawau Airport (TWU), Kota Kinabalu International Airport (BKI), Labuan Airport (LBU), and Sandakan Airport (SDK). Flights have begun to resume in recent days; however, lingering disruptions are possible as airlines work to clear the backlog of flights following the cancelations.

Additional small-scale eruptions could cause low-level seismic activity, ash clouds, pyroclastic flows, and landslides in the surrounding area. Road conditions could quickly deteriorate during periods of significant ashfall, and visibility could be reduced. Officials may close roads near the volcano depending on the presence of hazardous volcanic material. Fine particulate matter ejected from the volcano could continue to pose a hazard to flights in the surrounding airspace.

Further volcanic activity may impact air quality in North Sulawesi Province and neighboring areas. Individuals in the region - especially those with underlying pulmonary conditions such as asthma, chronic obstructive pulmonary disease (COPD), or lung cancers - may experience difficulty breathing and could suffer from lower tolerance to physical exertion.