Abert Rim in Lake County,

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 Idah ...

is one of the highest

fault scarp A fault scarp is a small step or offset on the ground surface where one side of a fault has moved vertically with respect to the other. It is the topographic expression of faulting attributed to the displacement of the land surface by movement al ...

s in the United States. It rises above the valley floor, finishing with an sheer-sided

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

cap. It was formed during the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...

epoch. At that time

ic flood lavas covered much of

eastern Oregon Eastern Oregon is the eastern part of the U.S. state of Oregon. It is not an officially recognized geographic entity; thus, the boundaries of the region vary according to context. It is sometimes understood to include only the eight easternmos ...

. In subsequent faulting, great blocks were tilted and Abert Rim is at the western end of one of these blocks, while

Lake Abert Lake Abert (also known as Abert Lake) is a large, shallow, alkali lake in Lake County, Oregon, United States. It is approximately long and wide at its widest point. It is located northeast of the small, unincorporated community of Valley Fall ...

lies on top of another. Stretching more than from Lakeview north to Alkali Lake, Abert Rim is also the longest exposed

in North America.

Bighorn sheep The bighorn sheep (''Ovis canadensis'') is a species of sheep native to North America. It is named for its large horns. A pair of horns might weigh up to ; the sheep typically weigh up to . Recent genetic testing indicates three distinct subspe ...

were transplanted to the rim in 1975 and 1977 from nearby

Hart Mountain Hart Mountain is a fault-block mountain, in Lake County, Oregon, U.S. It lies about to the east of Lakeview. It is sometimes confused with a mountain range, but is more properly described as a mountain. The two highest peaks are Warner Peak a ...

, and are often spotted from the Abert Rim geologic point of interest sign located along Highway 395. Raptors, such as the

Ferruginous Hawk The ferruginous hawk, (''Buteo regalis''), is a large bird of prey and belongs to the broad-winged buteo hawks. An old colloquial name is ferrugineous rough-leg, due to its similarity to the closely related rough-legged hawk (''B. lagopus''). ...

, are also common in the area. The

Chewaucan River The Chewaucan River is part of the Great Basin drainage. It flows through the Fremont–Winema National Forests, Bureau of Land Management land, and private property in southern Oregon. Its watershed consists of of conifer forest, marsh, an ...

enters

from the south, however it has no outlet. The lake level varies depending on rainfall and it nearly completely dried up 140 years ago. It is one of the Great Basin lakes. The escarpment and lake were first mapped on December 20, 1843, by John C. Frémont, who named it after Colonel

John James Abert John James Abert (17 September 1788 – 27 January 1863) was a United States soldier. He headed the Corps of Topographical Engineers for 32 years, during which time he organized the mapping of the American West. Abert was born in Shepherdstown ...

, his commanding officer. The southern section of Abert Rim is a popular spot for

paragliding Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched Glider (aircraft), glider aircraft with no rigid primary structure. The pilot sits in a :wikt:harness, harness o ...

and

hang gliding Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorised foot-launched heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covere ...

because of the frequent

thermal A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...

s created by warm valley air rising up against the cliffs. The area was formerly considered by many to be the hang gliding capital of the West until paragliding superseded it in popularity. National free flight festivals are held each year in late June and during the

Fourth of July Independence Day ( colloquially the Fourth of July) is a federal holiday in the United States commemorating the Declaration of Independence, which was ratified by the Second Continental Congress on July 4, 1776, establishing the United State ...

References

External links

* * Landforms of Lake County, Oregon Escarpments of the United States {{LakeCountyOR-geo-stub

See also

References

External links