Volcano Hazards Program

USGS-developed lahar detection systems provide warning of lahars

Scientists maintain an Acoustic Flow Monitor (AFM) at Mount St. Hel...

Scientists maintain an Acoustic Flow Monitor (AMF) at Mount St. Helens, Washington. It detects ground movement associated with lahars.

(Credit: Spicer, Kurt. Public domain.)

Scientists monitoring volcanoes face the critical challenge of detecting a potentially dangerous lahar as it is occurring so that public officials can issue warnings to people downstream. USGS scientists developed an inexpensive, durable, portable, and easily installed system to detect and continuously monitor the arrival and passage of debris flows and floods in river valleys draining active volcanoes.

The automated detection system relies on a series of solar-powered acoustic-flow monitor (AFM) stations installed in river valleys that are subject to frequent lahars. While typical seismometers are sometimes able to capture ground-shaking signals caused by lahars, AFMs are designed specifically to detect ground vibration from a lahar. Data from an AFM station are radio telemetered to a volcano observatory, where computer processing allows for automated data screening and notification warnings if the vibrations exceed a programmed threshold.

Acoustic Flow Monitor signal example from a small lahar in the earl...

Acoustic Flow Monitor signal example from a small lahar in the early morning of October 6, 2004. Ground vigrations (y-axis) increase as the lahar passes the station.

(Public domain.)

Learn more about monitoring lahars: