Pueblo Mountains

Pueblo Mountains
Pueblo Mountains south of Fields, Oregon
Highest point
Peak	Pueblo Mountain
Elevation	8,632 ft (2,631 m)
Coordinates	42°06′00″N 118°38′55″W / 42.1°N 118.6486°W / 42.1; -118.6486Coordinates: 42°06′00″N 118°38′55″W / 42.1°N 118.6486°W / 42.1; -118.6486
Dimensions
Length	30 mi (48 km) north–south
Width	22 mi (35 km) west–east
Area	356 sq mi (920 km2) including surrounding non-mountainous areas
Geography
Country	United States
States	Oregon and Nevada
Counties	Harney County, Oregon Humboldt County, Nevada
Geology
Age of rock	Triassic and Cretaceous
Type of rock	Uplifted sedimentary and volcanic

The Pueblo Mountains are a remote mountain range in the United States located mostly in southeastern Oregon and partially in northwestern Nevada. The highest point in the range is Pueblo Mountain. The dominant vegetation throughout is grasses and big sagebrush; however, there are meadows with cottonwood, aspen, and willow groves along some stream drainages. Most of the range is public land administered by the Bureau of Land Management. There is very little human development in the Pueblo Mountains, and most visitors come for backpacking cross-country, camping, and hunting.

The Pueblo Mountains in Harney County, Oregon, and Humboldt County, Nevada, are part of the Basin and Range Province of the Western United States, which is characterized by a series of parallel fault blocks forming long north–south-oriented mountain ranges separated by wide, high-desert valleys. The Steens-Pueblo block fault represents the northernmost extension of these structures. The Pueblo fault is not as massive as Steens Mountain; however, it is tilted at a 45-degree angle, a much greater angle than the Steens fault. This accounts for the relatively high elevation of the range's main ridgeline, which averages 7,300 feet (2,200 m) above sea level along its crest.

The mountains are composed of the same basalt that blankets much of southeastern Oregon. Much older metamorphic rocks lie under the more recent basalt flows. These older rocks are exposed along the range’s east-facing escarpment and may be related to some of the Triassic formations of the Blue Mountains to the north. These strata have diorite and granodiorite intrusions, probably formed in the Cretaceous Period. The southern part of the Pueblo Mountains has metamorphic rocks rich in quartz impregnated with gold, silver, and copper.