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Overview
Mount Jefferson is one of the major volcanic peaks of the Cascade Range. Most of the visible cone is less than 100,000 years old. A large explosive eruption left measurable ash deposits as far away as Idaho. The youngest lava flows on the mountain are less than 7,600 years old, since they postdate the great eruption that formed Crater Lake . There have been no eruptions in historic times and there isn't any current geothermal activity on the mountain. That doesn't mean that Mt. Jefferson is dead, though. It's regarded as a dormant volcano that will one day reawaken.
Trail Stats
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Photos
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Trail photo
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Trail photo
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