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Mount Jefferson

Jefferson

Stratovolcano · United States · 3199m

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.
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: Photo by Willie Scott, 1981 (U.S. Geological Survey). · Wikimedia Commons
Type
Stratovolcano
Country
United States
Region
North America Volcanic Regions / High Cascades Volcanic Arc
Elevation
3199m
Coordinates
44.674, -121.800
Last eruption
950
Tectonic setting
Subduction zone / Continental crust (> 25 km)
Landform
Composite
Major rock type
Andesite / Basaltic Andesite
Geological summary

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.

From Wikipedia

Mount Jefferson is a stratovolcano in the Cascade Volcanic Arc, part of the Cascade Range in the U.S. state of Oregon. The second highest mountain in Oregon, it is situated within Linn County, Jefferson County, and Marion County and forms part of the Mount Jefferson Wilderness. Due to the ruggedness of its surroundings, the mountain is one of the hardest volcanoes to reach in the Cascades. It is also a popular tourist destination despite its remoteness, with recreational activities including hiking, backpacking, mountaineering, and photography. Vegetation at Mount Jefferson is dominated by Douglas fir, silver fir, mountain hemlock, ponderosa pine, lodgepole pine, and several cedar species. Carnivores, insectivores, bats, rodents, deer, birds, and various other species inhabit the area.

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Eruption history

Summary (VEI over time)
Click a bar to see individual eruptions
4500 BCE~4305 BCE · 1 eruptions · max VEI ?755~950 · 1 eruptions · max VEI ?4500 BCE3137 BCE1775 BCE607 BCE755

Detailed timeline

  1. 950VEI ?Geological estimate
    950 – Ongoing
    S of Jefferson (South Cinder Peak)
  2. 4500 BCE (±50 yrs)VEI ?Geological estimate
    BCE 4500 – Ongoing
    SSE of Jefferson (Forked Butte)

External links

⚠ For reference only. Not for emergency response.