Mount Jefferson | U.S. Geological Survey
Source: https://www.usgs.gov/volcanoes/mount-jefferson
Archived: 2026-04-23 17:21
Mount Jefferson | U.S. Geological Survey
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Mount Jefferson
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Mount Jefferson
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Mount Jefferson (3,199 m, 10,495 ft) is the second tallest mountain in Oregon (after Mount Hood) and the only major volcanic center in the U.S. portion of the Cascade Range that hasn't erupted in the past 10,000 years.
Quick Facts
Location:
Oregon, Jefferson/Linn/Marion Counties
Latitude:
44.674° N
Longitude:
121.8° W
Elevation:
3,199 (m) 10,495 (f)
Volcano type:
Stratovolcano
Composition:
Andesite to Dacite
Most recent eruption:
During last glaciation ~15,000 years ago
Threat Potential:
Low/Very Low*
*based on the
National Volcano Early Warning System
Summary
The andesite-dacite stratovolcano was built in several stages between about 280 ka and 15 ka, with much of the edifice constructed in the past 100,000 years. The youngest additions to the main cone occurred in the interval from 30 to 20 ka—during the last ice age—and many of these flows show evidence of volcano-ice interaction. Remnants of andesite-dacite lavas at the margins of the volcano suggest that the Mount Jefferson area has been the site of predominantly andesite to dacite eruptions for at least the past 700,000 years.
Within about 15 km (9 mi) of the main cone, andesite and dacite have also erupted from at least 35 small vents, building many domes, small shields and lava aprons. The youngest lava flows in the area, though not associated with Mount Jefferson proper, are basaltic lava flows from four monogenetic vents (including Forked Butte) between 6 and 12 km (4 and 8 mi) south of Mount Jefferson. At least two of the flows postdate the 7.7 ka eruption of Mount Mazama. This relatively-young activity suggests that the area surrounding Mount Jefferson remains potentially active.
October 22, 2018
2018 update to the U.S. Geological Survey national volcanic threat assessment
2018 update to the U.S. Geological Survey national volcanic threat assessment
When erupting, all volcanoes pose a degree of risk to people and infrastructure, however, the risks are not equivalent from one volcano to another because of differences in eruptive style and geographic location. Assessing the relative threats posed by U.S. volcanoes identifies which volcanoes warrant the greatest risk-mitigation efforts by the U.S. Geological Survey and its partners...
Authors
John W. Ewert, Angela K. Diefenbach, David W. Ramsey
By
Volcano Hazards Program
,
Volcano Science Center
,
Agrigan
,
Ahyi Seamount
,
Alamagan
,
Anatahan
,
Asuncion
,
Belknap
,
Black Butte Crater Lava Field
,
Black Rock Desert Volcanic Field
,
Blue Lake Crater
,
Carrizozo Lava Flow
,
Cascade Range Weekly Update
,
Cinnamon Butte
,
Clear Lake Volcanic Field
,
Coso Volcanic Field
,
Crater Lake
,
Craters of the Moon Volcanic Field
,
Daikoku Seamount
,
Davis Lake Volcanic Field
,
Devils Garden Lava Field
,
Diamond Craters Volcanic Field
,
Dotsero Volcanic Center
,
East Diamante
,
Esmeralda Bank
,
Farallon de Pajaros
,
Fukujin Seamount
,
Glacier Peak
,
Guguan
,
Haleakalā
,
Hell's Half Acre Lava Field
,
Hualālai
,
Indian Heaven Volcanic Field
,
Jordan Craters Volcanic Field
,
Kama‘ehuakanaloa
,
Kasuga 2
,
Kīlauea
,
Lassen Volcanic Center
,
Long Valley Caldera
,
Mammoth Mountain
,
Markagunt Plateau Volcanic Field
,
Maug Islands
,
Mauna Kea
,
Mauna Loa
,
Medicine Lake
,
Mono Lake Volcanic Field
,
Mono-Inyo Craters
,
Mount Adams
,
Mount Bachelor
,
Mount Baker
,
Mount Hood
,
Mount Jefferson
,
Mount Rainier
,
Mount Shasta
,
Mount St. Helens
,
Newberry
,
Ofu-Olosega
,
Pagan
,
Red Hill-Quemado Volcanic Field
,
Ruby
,
Salton Buttes
,
San Francisco Volcanic Field
,
Sand Mountain Volcanic Field
,
Sarigan
,
Soda Lakes
,
South Sarigan Seamount
,
Supply Reef
,
Ta'u Island
,
Three Sisters
,
Tutuila Island
,
Ubehebe Craters
,
Uinkaret Volcanic Field
,
Valles Caldera
,
Wapi Lava Field
,
Weekly Update
,
West Crater Volcanic Field
,
Yellowstone
,
Zealandia Bank
,
Zuni-Bandera Volcanic Field
Quick Facts
Location:
Oregon, Jefferson/Linn/Marion Counties
Latitude:
44.674° N
Longitude:
121.8° W
Elevation:
3,199 (m) 10,495 (f)
Volcano type:
Stratovolcano
Composition:
Andesite to Dacite
Most recent eruption:
During last glaciation ~15,000 years ago
Threat Potential:
Low/Very Low*
*based on the
National Volcano Early Warning System
Volcanoes Hazards Program Links
Assess
Prepare
Forecast
Activity
Products
Observatories
About
Was this page helpful?
Skip to main content
Official websites use .gov
A
.gov
website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A
lock (
)
or
https://
means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Mount Jefferson
Find U.S. Volcano
Filters
Learn More
The map displays volcanoes, earthquakes, monitoring instruments, and past lava flows.
Get Help
Earthquake Plots
To view an earthquake cross-sectional plot, click "Draw Plot" to start drawing on the map. Once the plot area is selected, click on "View Plot" to view chart or "Clear Plot" to start over.
Map Layers
Earthquake Colors
Earthquake Depth Units
Earthquake Time Units
Results
Filters
Learn More
The map displays volcanoes, earthquakes, monitoring instruments, and past lava flows.
Get Help
Earthquake Plots
To view an earthquake cross-sectional plot, click "Draw Plot" to start drawing on the map. Once the plot area is selected, click on "View Plot" to view chart or "Clear Plot" to start over.
Settings
Map Layers
Earthquake Colors
Earthquake Depth Units
Earthquake Time Units
x
Map Legend
x
Map Legend
Results
Mount Jefferson
Home
Science
Multimedia
Publications
Connect
Mount Jefferson (3,199 m, 10,495 ft) is the second tallest mountain in Oregon (after Mount Hood) and the only major volcanic center in the U.S. portion of the Cascade Range that hasn't erupted in the past 10,000 years.
Quick Facts
Location:
Oregon, Jefferson/Linn/Marion Counties
Latitude:
44.674° N
Longitude:
121.8° W
Elevation:
3,199 (m) 10,495 (f)
Volcano type:
Stratovolcano
Composition:
Andesite to Dacite
Most recent eruption:
During last glaciation ~15,000 years ago
Threat Potential:
Low/Very Low*
*based on the
National Volcano Early Warning System
Summary
The andesite-dacite stratovolcano was built in several stages between about 280 ka and 15 ka, with much of the edifice constructed in the past 100,000 years. The youngest additions to the main cone occurred in the interval from 30 to 20 ka—during the last ice age—and many of these flows show evidence of volcano-ice interaction. Remnants of andesite-dacite lavas at the margins of the volcano suggest that the Mount Jefferson area has been the site of predominantly andesite to dacite eruptions for at least the past 700,000 years.
Within about 15 km (9 mi) of the main cone, andesite and dacite have also erupted from at least 35 small vents, building many domes, small shields and lava aprons. The youngest lava flows in the area, though not associated with Mount Jefferson proper, are basaltic lava flows from four monogenetic vents (including Forked Butte) between 6 and 12 km (4 and 8 mi) south of Mount Jefferson. At least two of the flows postdate the 7.7 ka eruption of Mount Mazama. This relatively-young activity suggests that the area surrounding Mount Jefferson remains potentially active.
October 22, 2018
2018 update to the U.S. Geological Survey national volcanic threat assessment
2018 update to the U.S. Geological Survey national volcanic threat assessment
When erupting, all volcanoes pose a degree of risk to people and infrastructure, however, the risks are not equivalent from one volcano to another because of differences in eruptive style and geographic location. Assessing the relative threats posed by U.S. volcanoes identifies which volcanoes warrant the greatest risk-mitigation efforts by the U.S. Geological Survey and its partners...
Authors
John W. Ewert, Angela K. Diefenbach, David W. Ramsey
By
Volcano Hazards Program
,
Volcano Science Center
,
Agrigan
,
Ahyi Seamount
,
Alamagan
,
Anatahan
,
Asuncion
,
Belknap
,
Black Butte Crater Lava Field
,
Black Rock Desert Volcanic Field
,
Blue Lake Crater
,
Carrizozo Lava Flow
,
Cascade Range Weekly Update
,
Cinnamon Butte
,
Clear Lake Volcanic Field
,
Coso Volcanic Field
,
Crater Lake
,
Craters of the Moon Volcanic Field
,
Daikoku Seamount
,
Davis Lake Volcanic Field
,
Devils Garden Lava Field
,
Diamond Craters Volcanic Field
,
Dotsero Volcanic Center
,
East Diamante
,
Esmeralda Bank
,
Farallon de Pajaros
,
Fukujin Seamount
,
Glacier Peak
,
Guguan
,
Haleakalā
,
Hell's Half Acre Lava Field
,
Hualālai
,
Indian Heaven Volcanic Field
,
Jordan Craters Volcanic Field
,
Kama‘ehuakanaloa
,
Kasuga 2
,
Kīlauea
,
Lassen Volcanic Center
,
Long Valley Caldera
,
Mammoth Mountain
,
Markagunt Plateau Volcanic Field
,
Maug Islands
,
Mauna Kea
,
Mauna Loa
,
Medicine Lake
,
Mono Lake Volcanic Field
,
Mono-Inyo Craters
,
Mount Adams
,
Mount Bachelor
,
Mount Baker
,
Mount Hood
,
Mount Jefferson
,
Mount Rainier
,
Mount Shasta
,
Mount St. Helens
,
Newberry
,
Ofu-Olosega
,
Pagan
,
Red Hill-Quemado Volcanic Field
,
Ruby
,
Salton Buttes
,
San Francisco Volcanic Field
,
Sand Mountain Volcanic Field
,
Sarigan
,
Soda Lakes
,
South Sarigan Seamount
,
Supply Reef
,
Ta'u Island
,
Three Sisters
,
Tutuila Island
,
Ubehebe Craters
,
Uinkaret Volcanic Field
,
Valles Caldera
,
Wapi Lava Field
,
Weekly Update
,
West Crater Volcanic Field
,
Yellowstone
,
Zealandia Bank
,
Zuni-Bandera Volcanic Field
Quick Facts
Location:
Oregon, Jefferson/Linn/Marion Counties
Latitude:
44.674° N
Longitude:
121.8° W
Elevation:
3,199 (m) 10,495 (f)
Volcano type:
Stratovolcano
Composition:
Andesite to Dacite
Most recent eruption:
During last glaciation ~15,000 years ago
Threat Potential:
Low/Very Low*
*based on the
National Volcano Early Warning System
Volcanoes Hazards Program Links
Assess
Prepare
Forecast
Activity
Products
Observatories
About
Was this page helpful?