Volcanic Ash

The InaSAFE Realtime Volcanic Ash page contains near real time volcanic ash impact assessments generated prior to or during recent volcanic ash eruption events in Indonesia.  The volcanic ash hazard models for ash thickness are prepared by Indonesia's Geological Agency, Badan Geologi to show the potential volcanic ash fallout on the ground. InaSAFE impact assessments are made automatically once a hazard map of forecast volcanic ash on the ground is uploaded to the server. This information is used by disaster managers to help them understand the potential scale of a volcanic ash impact and to recommend mitigation activities for the most vulnerable communities. This is particularly important in the lead up to an eruption when communities have an opportunity to prepare for a possible hazard event.

The InaSAFE Realtime Volcanic Ash platform allows users to see a list and map of the volcanic ash events for which a hazard data set has been uploaded. Volcanic ash events can be sorted or filtered by alert level, volcano name, date and time, eruption height and district. Users can zoom to a volcanic ash event and open the impact report. The platform also allows users to download the volcanic ash impact report, the original hazard data and the impact layer. The hazard data can be used in the desktop version of InaSAFE for further analysis.

The InaSAFE Realtime Volcanic Ash report shows details of the volcanic ash event such as the name and location of the volcano and the results of InaSAFE Realtime Volcanic Ash analysis. The analysis map shows the potential ash fallout classified into 5 classes of ash thickness on the ground:

  • between 0.01 and 0.1 cm,
  • between 0.1 and 2 cm,
  • between 2 and 5 cm,
  • between 5 and 10 cm,
  • greater than 10 cm

The InaSAFE Realtime Ash analysis report estimates the number of people in Indonesia exposed to each ash fallout class based on the thickness of ash on the ground; using a modelled estimate of 2015 population exposure data from World Pop. People are considered to be exposed if they are within the area of the event. The InaSAFE Realtime Volcanic Ash analysis also estimates the area of land cover affected, and lists nearby places and airports in the affected area by fallout level. 



Volcanic ash is modelled hazard data estimating the thickness of volcanic ash on the ground following a volcanic eruption. Volcanic ash thickness is modelled using volcano observations and forecast regional wind data. Each hazard layer is a single scenario model for one intensity of eruption and one wind model. Volcanic ash forecasts expire after 24 hours. This report does not include the potential impact of airborne volcanic ash on aviation services. 



  • The extent and severity of the modelled volcanic ash event may not be consistent with the actual event.
  • This report does not include the potential impact of airborne volcanic ash on aviation services. Nearby airports may already be affected or become affected in future by ash fall on the ground or other hazards.
  • Exposed population varies by the time (day or night, weekends, holidays etc.). Such variations are not considered in the estimates in InaSAFE.
  • The actual impact on people may differ from the analysis results due to limitations in the accuracy of the data, the analysis model and the behaviour of the local population. It does not include a measure of uncertainty.
  • For this reason, decisions should not be made solely on the information presented here and should always be verified by ground truthing and other reliable information sources.

More information:

For more information on the volcanic ash impact assessment in InaSAFE please refer to the online manual.