Mount Thielsen, or Big Cowhorn (Klamath: hisc’akwaleeʔas),[4] is an extinct shield volcano in the Oregon High Cascades, near Mount Bailey. Because eruptive activity ceased 250,000 years ago, glaciers have heavily eroded the volcano's structure, creating precipitous slopes and a horn-like peak. The spire-like shape of Thielsen attracts lightning strikes and creates fulgurite, an unusual mineral. The prominent horn forms a centerpiece for the Mount Thielsen Wilderness, a reserve for recreational activities such as skiing and hiking. Thielson is one of Oregon's Matterhorns.
Thielsen was produced by subduction of the Juan de Fuca Plate under the North American Plate.[5] Volcanism near the Cascades dates back to 55 million years ago (mya), and extends from British Columbia to California. Thielsen is part of the High Cascades, a branch of the main Cascades range that includes several Oregon volcanoes less than 3.5 million years old; it is also a member of a group of extinct volcanoes distinguished by their sharp peaks.
The area surrounding the volcano was originally inhabited by Klamath Native Americans, and was later encountered by settlers. One of the visitors was Jon Hurlburt, an early explorer of the area who named the volcano after the engineer Hans Thielsen. Later explorers discovered nearby Crater Lake. The volcano was not analyzed until 1884, when a team from the United States Geological Survey sampled its fulgurite deposits.
^ ab"Mt Thielsen". NGS Data Sheet. National Geodetic Survey, National Oceanic and Atmospheric Administration, United States Department of Commerce. Retrieved November 17, 2008.
^ ab"Mount Thielsen, Oregon". Peakbagger.com. Retrieved April 2, 2008.
^Andalkar, Amar (January 15, 2003). "Mount Thielsen". SkiMountaineer.com. Archived from the original on March 16, 2009. Retrieved March 29, 2009.
^"Klamath Tribes Language Project". The Klamath Tribes. 2012. Archived from the original on August 20, 2013. Retrieved March 21, 2016.
^Topinka, Lyn (December 15, 2004). "Cascade Range Volcanoes and Volcanics". Description. United States Geological Survey. Archived from the original on September 3, 2013.
MountThielsen, or Big Cowhorn (Klamath: hisc’akwaleeʔas), is an extinct shield volcano in the Oregon High Cascades, near Mount Bailey. Because eruptive...
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other Oregon volcanoes that were heavily glaciated—such as Mount Washington and MountThielsen—display eroded volcanic necks, Three Fingered Jack's present...
landmarks are visible from the summit, including Mount McLoughlin, MountThielsen, Union Peak, Mount Scott and the Klamath Basin. The trail ends next...
Oregon such as the Three Sisters 80 miles (130 km) north of Mazama and MountThielsen, also to the north. The Cleetwood trail leads for 1 mile (1.6 km) down...
220 ft (67 m)), and the high point of the trail is on a saddle north of MountThielsen (elevation 7,560 ft (2,304 m)). Altogether, there is 62,840 feet (19...
generally above 8,500 feet (2,600 m) on the steep northeast slope of MountThielsen, an extinct shield volcano. Lathrop Glacier consisted of two small bodies...
as the Three Sisters located 80 miles (130 km) north of Mazama and MountThielsen, also to the north. The Cleetwood trail leads for 1 mile (1.6 km) down...
Crater Lake National Park (15) Crater Lake Umpqua National Forest (13) MountThielsen Willamette National Forest (11) and Deschutes National Forest (12) Diamond...
15 km3 (3.6 cu mi) of basaltic andesite. Mount Bailey (north of Mount Mazama) MountThielsen (east of Mount Bailey) — highly eroded volcano with a prominent...
Dalrymple, G. B.; Smith, R. L. (March 1994). "Eruptive history and petrology of Mount Drum volcano, Wrangell Mountains, Alaska". Bulletin of Volcanology. 56 (1):...
in eastern Douglas County in the U.S. state of Oregon. It is in the MountThielsen Wilderness of the Umpqua National Forest, about 15 miles (24 km) west...
Mount Multnomah is an invalidated hypothetical ancient volcano postulated in a 1925 publication by geologist Edwin T. Hodge. It was proposed to exist...
Willamette NF) MountThielsen Wilderness (south; 40.36% in Umpqua NF and 47% in Winema NF) About 7,700 years ago, the eruption of Mount Mazama (forming...
well as high deserts and semi-arid shrublands. At 11,249 feet (3,429 m), Mount Hood is the state's highest point. Oregon's only national park, Crater Lake...
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