The Japan Meteorological Agency is investigating whether there is possibility of tsunami following the large eruption.

Mount Semeru Observation Post Officer,Mukdas Sofian said: ‘The ash column was observed to be gray with thick intensity to the north and northwest. At the time of this report,the eruption was still ongoing.’

Mukdas also urged residents to avoid being within a 2,500 metre radius of the crater to avoid any hot rock ejections that might occur.

Residents are urged to stay away from the volcano

He said: ‘The public is also asked to be aware of the potential for hot clouds,lava flows,and lahars (mudflow debris) along rivers/valleys that originate at the peak of Mount Semeru Volcano,especially along Besuk Kobokan,Besuk Bang,Besuk Kembar,and Besuk Sat,as well as the potential for lahars in the small rivers.’

How will the eruption affect flights?

The Australia Volcanic Ash Advisory Centre (VAAC) has issued a red aviation warning due to the 54,000ft ash plume which is moving at 30kts in a south-westerly direction.

A red aviation warning means that severe impacts are likely and action is required to stay safe.

With volcanoes,actions that are usually taken to ensure flight safety include diversions,cancellations and adjustments.

Volcanic ash can pose a significant threat to flight safety due to its hard and abrasive nature which can cause damage to engines,windows and other parts of aircrafts.

Indonesia's Mount Semeru has started to erupt. Currently the ash area extends up to FL540 (54,000ft/16,500 metres). More on Volcanic ash advisories (and how to enable them):https://t.co/LpLvhiEDmi pic.twitter.com/gk7jYw4Xnd

— Flightradar24 (@flightradar24) November 19,2025

In a translated written statement the East Java BPBD said: ‘The Rapid Response Team (TRC) of the Lumajang Regency BPBD carried out patrols and helped evacuate the elderly to safer places.

‘The pyroclastic flow is still ongoing,with a maximum amplitude of 40 mm. The pyroclastic flow reached a distance of 8.5 km from the mountain peak. The wind direction is towards the north.’

The Foreign Office states: ‘Indonesian authorities have set the alert level to 4 (of 4),warning of the potential for hot pyroclastic flows and lava flows along rivers,tributaries and valleys around Mount Semeru.’ 

In December 2021,the same volcano erupted,causing the deaths of at least 57 people.