Numerous, cooler springs lie to the south along the Alvord fault system. Hot waters are piped to a soaking pool that maintains temperatures of about 110° to 115° F. At Alvord Hot Springs, the best known and most accessible of the two, the natural springs emerge at a temperature of 180° to 170° F. Hot springs, including Alvord Hot Springs at the base of Steens Mountain and Mickey Hot Springs, near the Sheepshead Mountains to the northeast, rise through the thin, faulted crust. An archeological survey of the Alvord Basin, conducted by the University of Oregon in 1975, found a cultural record of human habitation spanning 10,000 years. At the close of the Ice Age, 13,000 to 14,000 years ago, a glacial outburst flood from Lake Alvord sent an estimated 40,000 cubic yards per second of water down the drainage of Crooked Creek and into the Owyhee River, dramatically lowering the lake level. Multiple, wave-carved shorelines from at least six episodes of filling and drainage can still be seen on the landscape, especially along the eastern side of the basin. Although many streams enter the basin, water can escape only through evaporation.ĭuring the Late Pliocene and Pleistocene, about 3.5 million to 15,000 years ago, Lake Alvord covered all of the present Alvord Desert. Tectonic activity has uplifted and tilted surrounding ranges, leaving the Alvord playa basin with only internal drainage. The Basin and Range geologic province is slowly extending westward, as faulting in and adjacent to the Alvord Desert remains active. Steens Mountain, at 9,773 feet, rises more than a mile above the Alvord Desert, where the average elevation is about 4,060 feet. It marks the easternmost part of Oregon’s Basin and Range.
Playa lakes are formed when rainwater fills shallow, round depressions in the landscape, leaving behind precipitated salt minerals on the earth’s crust upon evaporation. This fault-bounded flat basin is a graben-that is, a basin down-dropped by faulting-about 8 miles wide and 70 miles long. The Alvord Desert, east of the Pueblo Mountains and Steens Mountain and north of the towns of Andrews and Fields, is among the largest playa lakes in Oregon.
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