Jefferson
Stratovolcano in United States
Key Facts
Elevation
3,199 m (10,495 ft)
Type
Stratovolcano
Location
44.674°, -121.800°
Region
High Cascades Volcanic Arc
Rock Type
Andesite / Basaltic Andesite
Tectonic Setting
Subduction zone
Location
Loading map...
Overview
Mount Jefferson, Oregon's second highest peak, is a deeply eroded stratovolcano. The glacier-clad landmark prominent from both sides of the Cascade Range was named by Lewis and Clark for the president that sponsored their expedition. Jefferson was constructed in two episodes interrupted by extensive glacial erosion.
The first of these, beginning about 290,000 years ago, produced an andesitic-to-dacitic volcano possibly higher than the current summit. Dacitic lava domes were emplaced during a second cycle beginning about 70,000 years ago which included ash flows that traveled 15 km E and W. Several Holocene cinder cones near the Cascade crest south of Jefferson have produced lava flows that traveled down glacially carved valleys, including those from Forked Butte and North Cinder Peak.
The most recent eruption, from a cinder cone on the flank of the South Cinder Peak cone, produced a lava flow that traveled west into Marion Lake about 1,000 years ago.
Volcanic Hazards & Risk Assessment
Primary Hazards
- Pyroclastic flows
- Lava flows
- Volcanic bombs and ballistics
- Lahars and mudflows
Risk Level
Geological Composition & Structure
Rock Types
Tectonic Setting
Age & Formation
Eruption Statistics & Analysis
| Metric | Value | Global Ranking | Significance |
|---|---|---|---|
| Total Recorded Eruptions | Unknown | Low | Moderately active volcano |
| Maximum VEI | VEI Unknown | Minor | Local impact potential |
| Recent Activity | 1076 years ago | Historical | Historically active |
Monitoring & Alert Status
Monitoring Networks
Current Status
Nearby Volcanoes in North America Volcanic Regions
Quick Info
- •Smithsonian ID: 322020
- •Evidence: Eruption Dated
- •Epoch: Holocene
About the Photo
Volcanic activity at glacially eroded Mount Jefferson, Oregon's second highest peak, ended during the Pleistocene. However, scoria cones south of the volcano have been active as recently as about 1,000 years ago. The extensive Whitewater Glacier in the foreground has eroded deeply into the volcano across the E flank.
Photo by Willie Scott, 1981 (U.S. Geological Survey).
Authority Sources
Related Volcanoes
Basic Information
This page shows basic data from the Smithsonian Global Volcanism Program. For more detailed information, visit the official Smithsonian page.