How We Monitor Volcanoes

The USGS Volcano Hazards Program monitors volcanoes for signs of unrest (activity). We analyze and interpret the data we collect from our networks of instruments. The data and an understanding of what the data have meant in the past are crucial for determining when a volcano might erupt.

Most data can be accessed from our offices in the observatories but visits to the volcanoes, when possible, add valuable information.

When a volcano begins to show new or unusual signs of activity, our monitoring data help us answer critical questions necessary for assessing and then communicating timely information about volcanic hazards. For example, prior to the 2005 activity at Mount St. Helens our monitoring equipment recorded a large increase in earthquake activity. Scientists quickly examined other monitoring data including gas, ground deformation, and satellite imagery to assess if a magma or fluid was moving towards the surface. Based on the history of the volcano and the analysis of the monitoring data we were able to determine what types of materials could be moving towards the surface. The possible magma and fluid compositions helped us figure out what types of hazards could potentially occur. The possible types of hazards help determine what real-time warnings are needed to prevent loss of life and property damage.

Types of Monitoring Techniques

image of different types of volcano monitoring techniques