Active volcanoes are complex natural systems, and understanding a volcano's behaviors requires the attention of specialists from many science disciplines. It demands a combination of current knowledge about magma systems, tectonic plate motion, volcano deformation, earthquakes, gases, chemistry, volcano histories, processes, and hazards.
No single tool or technique can adequately monitor or predict volcanic behaviors. Therefore, volcanologists rely on an assortment of instruments and techniques to monitor volcanic unrest. This requires placement of monitoring instruments both close to and far away from the primary source of eruptive activity (e.g. in a crater, on the crater rim, and on the volcano's flanks). By placing sensitive monitoring instruments at hazardous volcanoes in advance of the unrest, the USGS CVO helps to ensure that communities at risk can be forewarned with sufficient time to prepare and implement response plans and mitigation measures. Recommendations for the numbers and types of ground-based sensors were made by an interdisciplinary team of scientists as part of planning for the National Volcano Early Warning System. CVO uses these recommendations to plan monitoring improvements throughout the Cascades.
The events surrounding the May 18, 1980 eruption of Mount St. Helens helped scientists to recognize some new and subtle patterns of volcanic activity that could help them forecast Cascade volcanoes' eruptions. Since then, tools for tracking the movement of magma beneath Cascade volcanoes have evolved from the use of isolated instruments to dense networks of ground-based sensors that measure earthquakes, swelling of the volcano, and emission of volcanic gases.
Today, scientists rely upon remote monitoring equipment 24 hours a day and 365 days a year to deliver real-time data to the CVO. When scientists design and install monitoring stations on the Cascade volcanoes, they must consider the remoteness of sites, rough terrain, and wintry conditions. Each monitoring station contains delicate sensors, a power unit, and an antenna that can withstand strong winds, heavy snowpack, and sub-zero temperatures. Just as important to the monitoring devices are telemetry systems designed to transmit data from each volcano to the CVO. The systems are developed to relay radio signals reliably, unimpeded by miles of rugged mountainous terrain.
During the past decade at Cascade volcanoes, USGS and the Pacific Northwest Seismograph Network (PNSN) have expanded monitoring networks on Mount St. Helens, Mount Rainier, Mount Hood, Newberry Volcano, and Crater Lake. CVO currently has plans in development to augment sparse monitoring on other hazardous Cascade volcanoes including Mount Baker and Glacier Peak. You might see these instruments on a volcano's slopes; please know that they are hard at work for communities downwind and downstream of the volcano.