Oregon, United States
Mount Thielsen, or Big Cowhorn, is an extinct shield volcano in the Oregon High Cascades, near Mount Bailey. Mount Thielsen stopped erupting 250,000 years ago, and subsequent glacial erosion has formed a horn-like shape. The spire-like shape of Thielsen attracts lightning strikes and causes the formation of fulgurite, an unusual mineral. The prominent horn forms a centerpiece for the Mount Thielsen Wilderness, an area with many recreational activities.
History and geography
The area was previously inhabited by Native Americans, who referred to the mountain as "Hischokwolas". The volcano's current name was coined by Jon Hurlburt, a Polish explorer. The man dedicated the name to Hans Thielsen, a railroad engineer and builder known in the area.
Diamond Lake lies to the west of Mount Thielsen and beyond lies Mount Bailey, a much less eroded and younger stratovolcano. Its sharp peak is a prominent feature of the skyline visible from Crater Lake National Park. Both of the volcanoes are part of the Oregon High Cascades, a range that sections off the stratovolcanoes of Oregon that are younger than 3.5 million years. The High Cascades include Mount Jefferson, the Three Sisters, Broken Top, and other stratovolcanos and remnants.