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Volcanoes pose many hazards to their surroundings, from ashfall, mudflows, lava flows, landslides, and associated earthquakes.  At least 54 of the United States' 169 active volcanoes pose major threats to public health and safety and to major industries such as agriculture, aviation, and transportation.


Ash from Mt. Redoubt, a remote volcano in Alaska, can threaten many aviation routes.Image Credit: U.S. Geological Survey/Photo by R.G. McGinsey

An explosive volcano can devastate its local area with mudflows, lava flows, and avalanches of hot rock and gas. Mudflows from ice-clad volcanoes like Mt. Rainier can travel tens of miles from the volcano. Some volcanic hazards, such as ash fall, can even impact areas hundreds of miles away. While it is not possible to forecast the exact time and place of an eruption, volcano monitoring is important in order to detect changes in a volcano's activity and provide warning of potential eruptions.   Read more

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Case Studies & Factsheets

Fig. 1. Although Glacier Peak normally can not be seen from any urban areas, this active volcano periodically erupts in an explosive catastrophic manner that could affect the lower part of the populated Skagit River Valley. Credit: D. Mullineaux, USGS

Surface and subsurface mapping of lahar and lahar runout deposits from Glacier Peak volcano has contributed important geologic information for land-management planning and emergency preparedness in the lower Skagit Valley. Defining the Problem Active volcanoes, such as Glacier Peak (Fig. 1), pose a...


More than just volcanic eruptions Volcanic eruptions are a serious hazard. But at many stratovolcanoes in Washington, Oregon, Northern California, and Alaska, landslides and debris flows can be just as dangerous. Some of these - especially volcanic mudflows (lahars) - are directly triggered by...