Deschutes & Ochoco National Forests
Crooked River National Grassland

Oregon Volcanoes

Mt. Jefferson Volcano

SUMMARY

Type: stratovolcano
Activity: extinct??
Last Eruption: about 70,000 yrs ago
Rock Type: andesite to dacite
Eruptive Volume: 25 cu km
Latitude: 44.68 N
Longitude: 121.80 W
Location Maps: from TIGER Mapping Service

• State Level - shows state and communities
• County Level - shows county lines, highways, and communities
• Local Level - shows above plus lakes and local roads

Topo Map from TopoZone

Mt. Jefferson Photo Menu

GEOLOGIC BACKGROUND:

Mt. Jefferson is a composite cone of basaltic andesite, andesite, and dacite erupted on several overlapping basaltic shield volcanoes. Mt. Jefferson has erupted repeatedly for hundreds of thousands of years, with its last eruptive episode during the last major glaciation which culminated about 15,000 years ago. Geologic evidence shows that Mt. Jefferson is capable of large explosive eruptions. The largest such eruption occurred between 35,000 and 100,000 years ago, and caused ash to fall as far away as the present-day town of Arco in southeast Idaho.

HISTORIC ACTIVITY:

• None

DATA SOURCE:

• USGS
  

ADDITIONAL INFORMATION

• Link to U.S.G.S. - CVO's Mt. Jefferson Info
• Link to U.S.G.S. Visit a Volcano Info for Mt. Jefferson
• Link to Volcano World's Mt. Jefferson Info