World Library  
Flag as Inappropriate
Email this Article
 

Broken Top

Broken Top
Elevation 9,175 ft (2,797 m)[1]
Prominence 2,175 ft (663 m)[1]
Location
Location Deschutes County, Oregon, U.S.
Range Cascade Range
Coordinates [2]
Topo map USGS Broken Top
Geology
Type Stratovolcano
Age of rock Pleistocene
Volcanic arc Cascade Volcanic Arc
Last eruption About 100,000 years ago[3]

Broken Top is an extinct, glacially eroded stratovolcano in Oregon,[4] part of the extensive Cascade Range. Located southeast of the Three Sisters peaks, the volcano, residing within the Three Sisters Wilderness,[5] is 20 miles (32 km) west of Bend, Oregon in Deschutes County. Eruptive activity stopped roughly 100,000 years ago, and currently, erosion by glaciers has reduced the volcano's cone to where its contents are exposed. Bend and Crook Glaciers are the two named glaciers on the peak.

Contents

  • Geology 1
  • Wilderness 2
  • See also 3
  • References 4
  • External links 5

Geology

Broken Top. USGS image.

Due to extensive erosion, the contents of Broken Top's cone are exposed, which allows volcanologists to classify Broken Top as a complex stratovolcano.[4] Its initial eruptions during the Pleistocene, consisting of basaltic andesite lava, contributed to a base shield. The center of this edifice consists of agglomerate, which was oxidized, and intrusive dikes and geologic sills.[4] Erratic eruptions continued afterward, erupting silicic lava. Much of the current cone is occupied by flows of andesite, dacite, rhyodacite, and pyroclastic flows; these deposits extending from the subordinate volcano to the summit. The volcanic crater, now 0.8 km, was most likely created through subsidence.[4]

Wilderness

Broken Top resides in the Three Sisters Wilderness, which makes up 242,000 acres (980 km2) of the Willamette National Forest. About the area, there are geologic features such as Collier Glacier, Rock Mesa, Collier Cone, and Yapoah Crater.

Permits for average entry are distributed, free, from Memorial Day (May 31)–Halloween (October 31).[6] To gain access to the Obsidian area of the wilderness, special entry is required, for both day and overnight hikers.[6] These passes are distributed only at McKenzie Ranger District in Willamette Forest and Sisters Ranger District in Deschutes Forest.[6] The administration disallows any vehicle entry.

See also

References

  1. ^ a b
  2. ^
  3. ^
  4. ^ a b c d
  5. ^
  6. ^ a b c

External links

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from World Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.