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Jefferson

Photo of this volcano
  • Country
  • Volcanic Region
  • Landform | Volc Type
  • Last Known Eruption
  • 44.674°N
  • 121.8°W

  • 3,199 m
    10,495 ft

  • 322020
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

The Global Volcanism Program has no activity reports available for Jefferson.

The Global Volcanism Program has no Weekly Reports available for Jefferson.

The Global Volcanism Program has no Bulletin Reports available for Jefferson.

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Eruptive History

There is data available for 2 confirmed Holocene eruptive periods.

0950 (?) Confirmed Eruption  

Episode 1 | Eruption S of Jefferson (South Cinder Peak)
0950 (?) - Unknown Evidence from Sidereal: Varve Count

List of 4 Events for Episode 1 at S of Jefferson (South Cinder Peak)

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Lava flow
   - - - -    - - - - Cinder Cone
   - - - -    - - - - Scoria

4500 BCE ± 50 years Confirmed Eruption  

Episode 1 | Eruption SSE of Jefferson (Forked Butte)
4500 BCE ± 50 years - Unknown Evidence from Sidereal: Varve Count

List of 4 Events for Episode 1 at SSE of Jefferson (Forked Butte)

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Lava flow
   - - - -    - - - - Cinder Cone
   - - - -    - - - - Tephra
Deformation History

There is no Deformation History data available for Jefferson.

Emission History

There is no Emissions History data available for Jefferson.

Photo Gallery

The western slopes of Mount Jefferson rise above forested hills composed of older Pleistocene volcanic rocks. Scoria cones younger than the eroded main edifice, which ceased activity during the late Pleistocene, are located to the south.

Photo by Lee Siebert, 1982 (Smithsonian Institution).
Mount Jefferson is seen to the south from Olallie Butte. The Three Sisters and Broken Top volcanoes are on the horizon to the left. Within 15 km from the main edifice domes and lava flows have erupted from at least 35 vents.

Photo by Lee Siebert, 1995 (Smithsonian Institution).
Mount Jefferson rises above Breitenbush Lake to the north. The glacially eroded volcano has not erupted since the late Pleistocene, although flank vents to the south that are not associated with the main edifice have been active since 7,700 years ago.

Photo by Lee Siebert, 1995 (Smithsonian Institution).
Mount Jefferson of the central Oregon Cascades rises above deep canyons eroded into thick lava flows of the Columbia River Basalt formation that covers a large area to the NE.

Photo by Richard Waitt, 1984 (U.S. Geological Survey).
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).
Mount Jefferson in the center and Mount Hood to the right, seen from Broken Top volcano to the south, are the two highest peaks in Oregon, towering above lower volcanic peaks of the High Cascades, such as Black Butte in the foreground. Mount Hood has been active in historical time and Mount Jefferson has Holocene scoria cones to its south, although previous eruptions of the main edifice occurred during the late Pleistocene.

Photo by Lee Siebert, 1982 (Smithsonian Institution).
The unnamed scoria cone to the lower right, viewed from Bear Butte to the NW, was the source of a 13-km-long lava flow that traveled to the west down Jefferson Creek in the center of the photo. The lava flow overlies the northern lobe of a 6,500-year-old flow from Forked Butte, another Holocene scoria cone south of Mount Jefferson. The Forked Butte lava flow divided into lobes that traveled on either side of Sugar Pine Ridge in the background.

Photo by Willie Scott, 1972 (U.S. Geological Survey).
The Jefferson Creek lava flow traveled 13 km down Jefferson and Candle Creeks from an unnamed cinder cone NE of Forked Butte and is younger than the nearby 6,500-year-old Forked Butte lava flow. The two flows traveled down different drainages and joined near this point. The snow-covered summit of Mount Jefferson is visible above the trees.

Photo by Lee Siebert, 1995 (Smithsonian Institution).
Forked Butte, the scoria cone on the left skyline south of snow-capped Mount Jefferson, formed about 6,500 years ago. It produced lava that flowed from the notch to the right of Forked Butte down valleys on both sides of Sugar Pine Ridge that forms the right skyline. The southern lobe traveled 8 km to the west down Cabot Creek below Sugar Pine Ridge.

Photo by Lee Siebert, 1995 (Smithsonian Institution).
Forked Butte, viewed here from the SW, is a Holocene scoria cone south of Mount Jefferson that produced an 8-km-long lava flow down Cabot Creek about 6,500 years ago. Forked Butte is one of three cones south of Jefferson that have produced Holocene lava flows.

Photo by Willie Scott, 1973 (U.S. Geological Survey).
Forked Butte scoria cone in the foreground formed about 6,500 years ago south of Mount Jefferson, whose flank appears to the right. A lava flow from the southern base of Forked Butte traveled 8 km to the west down Cabot Creek.

Photo by Dan Miller, 1977 (U.S. Geological Survey).
Snow-covered Forked Butte scoria cone in the center of the photo rises above the valley floor across from Bear Butte on the NE. A lava flow that was emplaced about 6,500 years ago can be seen down the left flank of the cone, one of two lobes that split around either side of Sugar Pine Ridge to the far left.

Photo by Willie Scott, 1972 (U.S. Geological Survey).
The latest eruption in the Mount Jefferson area occurred from the scoria cone at the lower left on the flank of South Cinder Peak in the center of the photo. The eruption, dated to about 1,000 years ago, formed the cone and produced a lava flow that split into two lobes. One traveled to the NW, and the other flowed 3.5 km W into Marion Lake.

Photo by Willie Scott, 1973 (U.S. Geological Survey).
South Cinder Peak, the unvegetated scoria cone near the center of the photo, is the youngest volcanic feature in the Mount Jefferson area. A smaller cinder cone seen at the left on its south flank in this view from the SE, formed about 1,000 years ago and produced a lava flow that traveled to the west.

Photo by Dan Miller, 1977 (U.S. Geological Survey).
Mount Jefferson has been inactive since the late Pleistocene and shows the effect of extensive erosion by glaciers. The Jefferson Park Glacier on the N flank in the foreground and the Whitewater Glacier on the E flank are the two largest on Jefferson.

Photo by Dan Miller, 1977 (U.S. Geological Survey).
The lava flow in the foreground, with snow-capped Mount Jefferson in the background, was emplaced about 2,600-2,900 years ago from Yapoah scoria cone on the north flank of North Sister. Lava flows in the middle of the photo originated from the Little Belknap shield volcano, part of one of the largest concentrations of recent volcanism in the continental United States: the McKenzie Pass area of the central Oregon Cascade Range.

Photo by Lee Siebert, 1995 (Smithsonian Institution).
The steep summit pinnacle of Mount Jefferson, seen here from the south, is one of the most dramatic summits of a Cascade Range volcano. Jefferson has been inactive since the late Pleistocene, allowing glacial erosion to remove much of the original summit and exposing the more erosion-resistant rocks that cooled slowly in the central conduit.

Photo by Lee Siebert, 1996 (Smithsonian Institution).
Deep glacial valleys cut the western flanks of Mount Jefferson. The original edifice was extensively eroded by glaciers prior to formation of a younger dacite cone on top of the older edifice. Lava dome growth was associated with the younger volcano and were accompanied by major ash-producing eruptions and pyroclastic flows, before activity ceased activity during the late Pleistocene.

Photo by Lee Siebert, 1996 (Smithsonian Institution)
Snow-capped Mount Jefferson rises above Detroit Lake, a hydroelectric reservoir NW of the volcano. The Mount Jefferson region is a popular recreational area in the central Cascades and is in the Mount Jefferson Wilderness Area.

Photo by Lee Siebert, 2000 (Smithsonian Institution)
GVP Map Holdings

Maps are not currently available due to technical issues.

The maps shown below have been scanned from the GVP map archives and include the volcano on this page. Clicking on the small images will load the full 300 dpi map. Very small-scale maps (such as world maps) are not included.

Smithsonian Sample Collections Database

There are no samples for Jefferson in the Smithsonian's NMNH Department of Mineral Sciences Rock and Ore collection.

External Sites