Our studies tell us a lot about how Mount Shasta has behaved in the past, going back as far as an older volcano that was destroyed by a huge avalanche about 300,000 years ago and coming up to our own experiences. Have we been able to come to some conclusions about whether Mount Shasta is dangerous? Yes, we have. It seems fair to assume that its most likely future behavior will be much like its past behavior. We have shown that Mount Shasta is an active volcano–it erupted only about 200 years ago and has erupted many times in the past few thousand years. We know that it has undergone periods of major cone building; these were periods of nearly continuous lava-flow eruptions and associated explosive and other disruptive events that lasted for centuries or millennia. We know it is capable of causing serious damage even without an eruption. At the same time, we think that repetitions of some of the most drastic past events, such as catastrophic destruction by a huge avalanche, while possible, are rather unlikely.

We can use the knowledge gained from our studies at Mount Shasta to estimate the probabilities that certain types of events will occur again in the near future. Probabilities can be used for making decisions about land use, insurance, and other long-term needs. We are mapping out the areas most likely to be affected by particular kinds of volcano-related events so authorities can plan how to respond to them in the future. And monitoring can detect any signs that the volcanic system gives about impending changes–things like swarms of microearthquakes, deformation of the ground surface, or changes in the composition of fumaroles or ground water. Armed with these types of information, the citizens of Mount Shasta's surrounding communities and the authorities responsible for managing the land resources or maintaining the infrastructure of modern transportation, communications, and emergency-response planning can be informed to help them make wise decisions, both for the long range and in the event of a return to activity by our largest stratocone volcano.

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Sources of additional information on Mount Shasta

URL of this page: http://volcanoes.usgs.gov/Hazards/Where/ShastaDanger/TheAnswer.html