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Mount Jefferson

From Portland Hikers Field Guide

Mt. Jefferson from Olallie Lake, some ten miles north of the mountain. (Matt Reeder)


Volcanic History

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.

Human History

Mount Jefferson was named by Lewis and Clark when they noticed it from near the mouth of the Willamette River.

Climbing information

Mount Jefferson is a quite difficult climb. While it's shorter than Mount Hood, the climb takes a lot of technical expertise including a very steep snow climb and a 400 foot rock pinnacle at the very summit.

Trip Reports

Related Discussions / Q&A

Guidebooks that cover this destination

More Links

Summit Post's Mount Jefferson page.


Portland Hikers Field Guide is built as a collaborative effort by its user community. While we make every effort to fact-check, information found here should be considered anecdotal. You should cross-check against other references before planning a hike. Trail routing and conditions are subject to change. Please contact us if you notice errors on this page.