Note: This VAL system was in use from October 2004–October 2006. The current VAL system can be found here.
Agency: United States Geological Survey (USGS)
Name: Notification of Ash Hazards to Aircraft
Elements of VAL system
| Domain | Aviation |
| Volcano | Cascades |
| Scheme range | 4-level scale |
| Lowest level | 1 |
| Highest level | 4 |
| Level name type | Color |
| Level for lack/loss of monitoring | No |
| Volcanic activity | Yes |
| Hazards possible | Yes |
| Locations affected | Yes |
| Potential impacts | No |
| Forecast language | Yes |
| Timing language | Yes |
| Actions to take | No |
| Agency actions | No |
| Link to evacuations | No |
| Reporting frequency per level | No |
| Link to monitoring thresholds | No |
| Step-up and step-down language | No |
Related References
Fearnley, C. J., McGuire, W. J., Davies, G., & Twigg, J. (2012). Standardisation of the USGS Volcano Alert Level System (VALS): analysis and ramifications. Bulletin of Volcanology, 74(9), 2023-2036. https://doi.org/10.1007/s00445-012-0645-6
Scott, W. E., Sherrod, D. R., & Gardner, C. A. (1750). Overview of the 2004 to 2006, and continuing, eruption of Mount St. Helens, Washington. US Geological Survey Professional Paper, pg. 7. https://doi.org/10.3133/pp17501