Union Peak is a heavily eroded shield volcano in the Cascade Range of central

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idaho. T ...

, located along the Cascade Crest less than southwest of the rim of

Crater Lake Crater Lake ( Klamath: ''Giiwas'') is a volcanic crater lake in south-central Oregon in the western United States. It is the main feature of Crater Lake National Park and is famous for its deep blue color and water clarity. The lake partly fill ...

Ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...

glaciers eroded away most of the flanks of the volcano, leaving numerous deep

cirques A (; from the Latin word ') is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie (from Scottish Gaelic , meaning a pot or cauldron) and (; ). A cirque may also be a similarly shaped landform ...

surrounding a central

glacial horn A pyramidal peak, sometimes called a glacial horn in extreme cases, is an angular, sharply pointed mountain peak which results from the cirque erosion due to multiple glaciers diverging from a central point. Pyramidal peaks are often examples o ...

. This is the same process that formed the summit horns of

Three Fingered Jack Three Fingered Jack is a summit of a shield volcano of the Cascade Range in the U.S. state of Oregon. Formed during the Pleistocene epoch, the mountain consists mainly of basaltic andesite lava and was heavily glaciated in the past. While o ...

Mount Washington Mount Washington is the highest peak in the Northeastern United States at and the most topographically prominent mountain east of the Mississippi River. The mountain is notorious for its erratic weather. On the afternoon of April 12, 1934 ...

, Howlock Mountain, and Mount Thielsen from other shield volcanoes farther north in the Oregon Cascades. Union Peak is located within

Crater Lake National Park Crater Lake National Park is an American national park located in southern Oregon. Established in 1902, Crater Lake is the fifth-oldest national park in the United States and the only national park in Oregon. The park encompasses the caldera of ...

, and the summit was used as a post for

fire lookout A fire lookout (partly also called a fire watcher) is a person assigned the duty to look for fire from atop a building known as a fire lookout tower. These towers are used in remote areas, normally on mountain tops with high elevation and a ...

s from the 1930s to the 1950s. A

trail A trail, also known as a path or track, is an unpaved lane or small road usually passing through a natural area. In the United Kingdom and the Republic of Ireland, a path or footpath is the preferred term for a pedestrian or hiking trail. ...

leads to the summit from the

Pacific Crest Trail The Pacific Crest Trail (PCT), officially designated as the Pacific Crest National Scenic Trail, is a long-distance hiking and equestrian trail closely aligned with the highest portion of the Cascade and Sierra Nevada mountain ranges, which lie ...

off

Oregon Route 62 Oregon Route 62 is an Oregon state highway that runs between the city of Medford, and U.S. Route 97 between Chiloquin and Klamath Falls. The highway approaches Crater Lake National Park from the south, and is known as the Crater Lake Highway. W ...

References

* * * * {{Crater Lake Crater Lake National Park Shield volcanoes of the United States Subduction volcanoes Cascade Volcanoes Volcanoes of Oregon Mountains of Oregon Landmarks in Oregon Cascade Range Mountains of Klamath County, Oregon Volcanoes of Klamath County, Oregon