A Dangerous Combination Large parts of most Cascade volcanoes are covered with permanent snow and ice that pose a special hazard during periods of volcanic unrest. Even small eruptions can melt a large amount of snow and ice, triggering debris flows that can travel tens of miles beyond the flanks of the volcano into populated valleys. Years after volcanic unrest has stopped, erosion of deposits can cause increased sediment that clogs waterways, disrupts aquatic ecosystems, and worsens flooding. Debris flows are the most costly effects of eruptions at snow-clad volcanoes. This information helps scientists to better anticipate future activity at a volcano, and provides a basis for mitigating the effects of future eruptions through land-use and emergency planning.
Volcanoes often show signs that they are getting ready to erupt days to months in advance.
Seismic activity, ground movements, and gas emissions at Cascade volcanoes are monitored by CVO in order to detect subtle changes that may herald the next eruption. Seismic activity is continuously monitored under the auspices of the USGS Volcano Hazards and Geothermal Studies Program through CVO, the USGS in Menlo Park, California, and the University of Washington Geophysics Program in Seattle, Washington. When volcanic activity increases, CVO issues advisories, warnings, and whenever possible, specific predictions concerning eruptions and their potential impacts. Related research topics include dynamics of debris flows, effects of volcanic gases on weather and climate, and effects of increased sediment transport on streams. New instrumentation, software, and hardware developed by the USGS enable scientists to acquire, process, and interpret data more quickly and effectively than ever before.